Objective c - Why my Memory Usage when running App on IPhone Device using Xcode increases rapidly

Question

My App makes a recursive call every 2 seconds using NSTimer, now i have 3 NSTimers making recursive calls. when i take these timers out the app runs fine and memory usage is not increasing rapidly but still increasing slowly. Ok now that the NSTimers are out i still get Memory Usage going up and this is my find on Instruments:

Not sure what to do next to find the memory usage going up, can anyone point me to the right directions, i will show code as well if needed.

If i add my timers back this is the recursive call being made by the three timers:

-(NSString*)setupPhpCall:(NSString*)requestString :(NSString*)sciptPage{
@autoreleasepool {

    NSURLCache *sharedCache = [[NSURLCache alloc] initWithMemoryCapacity:0 diskCapacity:0 diskPath:0];
    [NSURLCache setSharedURLCache:sharedCache];


    NSData *myRequestData = [NSData dataWithBytes: [requestString UTF8String] length: [requestString length]];

    // Create your request string with parameter name as defined in PHP file
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: [NSString stringWithFormat: @"http://www.xxx.co.uk/%@", sciptPage]]];
    // set Request Type
    [request setHTTPMethod: @"POST"];
    // Set content-type
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"content-type"];
    // Set Request Body
    [request setHTTPBody: myRequestData];
    // Now send a request and get Response

    NSHTTPURLResponse* urlResponse = nil;
    NSError *error = nil;


    NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:&urlResponse error: &error];
    // Log Response

    [sharedCache removeAllCachedResponses];

    NSString *response = [[NSString alloc] initWithBytes:[returnData bytes] length:[returnData length] encoding:NSUTF8StringEncoding];
    //NSLog(@"%@",response);


    return response;

}
return @"";
}

This is what the timer runs every two seconds:

-(void)recurseForumActivity:(NSTimer *)timer{
@autoreleasepool {
    __weak dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_async(concurrentQueue, ^{


         myRequestStringForum = [NSString stringWithFormat:@"lastDate=%@&threadTitle=%@&threadCountry=%@&threadCategory=%@&threadSubCategory=%@&getData=0",lastDateForumActivity,searchThreadTitle, searchThreadCountry, searchThreadCategory, searchThreadSubCategory];
         responseForum = [self setupPhpCall:myRequestStringForum :@"xxx.php"];

        dispatch_async(dispatch_get_main_queue(), ^{

            if(responseForum.length > 0 && ![responseForum isEqualToString:@"[]"]){

                labelNewForumThreads.text = [NSString stringWithFormat:@"%@ new threads...", responseForum];







                if(imageviewForumAlert == NULL){
                    UIImage *image = [UIImage imageNamed:@"alert.png"];

                    imageviewForumAlert = [UIImageView new];
                    [viewNav1 addSubview:imageviewForumAlert];
                    imageviewForumAlert.translatesAutoresizingMaskIntoConstraints = NO;
                    imageviewForumAlert.image = image;

                    NSDictionary *viewsDictionary = @{@"imageviewForumAlert":imageviewForumAlert};
                    NSArray *constraint_H = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-19-[imageviewForumAlert(12)]-19-|"
                                                                                    options:0
                                                                                    metrics:nil
                                                                                      views:viewsDictionary];

                    NSArray *constraint_V = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-19-[imageviewForumAlert(12)]-19-|"
                                                                                    options:0
                                                                                    metrics:nil
                                                                                      views:viewsDictionary];



                    [self.view addConstraints:constraint_H];
                    [self.view addConstraints:constraint_V];



                }else{
                    imageviewForumAlert.hidden = NO;

                }
                /**NSDictionary *dic = [response JSONValue];
                if((NSNull*)dic != [NSNull null]){

                    labelNewForumThreads.text = [NSString stringWithFormat:@"%d new threads...", dic.count];

                }**/

            }else{

                imageviewForumAlert.hidden = YES;



                labelNewForumThreads.text = [NSString stringWithFormat:@"%d new threads...", 0];
            }
            /**else{
                labelNewForumThreads.text = [NSString stringWithFormat:@"%d new threads...", 0];
            }**/

        });

    });
}

}

EDIT

I have modified the recursive call to this and has stopped memory increasing rapidly but still goes up slowly, i have added this to give the call some time [NSThread sleepForTimeInterval:2.0f]:

-(void)recurseForumActivity{
@autoreleasepool {
    __weak dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_async(concurrentQueue, ^{


         myRequestStringForum = [NSString stringWithFormat:@"lastDate=%@&threadTitle=%@&threadCountry=%@&threadCategory=%@&threadSubCategory=%@&getData=0",lastDateForumActivity,searchThreadTitle, searchThreadCountry, searchThreadCategory, searchThreadSubCategory];
         responseForum = [self setupPhpCall:myRequestStringForum :@"getThreadRecurse.php"];

            [NSThread sleepForTimeInterval:2.0f]; // waits 2 seconds then gives the response

        dispatch_async(dispatch_get_main_queue(), ^{

            if(responseForum.length > 0 && ![responseForum isEqualToString:@"[]"]){

                labelNewForumThreads.text = [NSString stringWithFormat:@"%@ new threads...", responseForum];







                if(imageviewForumAlert == NULL){
                    UIImage *image = [UIImage imageNamed:@"alert.png"];

                    imageviewForumAlert = [UIImageView new];
                    [viewNav1 addSubview:imageviewForumAlert];
                    imageviewForumAlert.translatesAutoresizingMaskIntoConstraints = NO;
                    imageviewForumAlert.image = image;

                    NSDictionary *viewsDictionary = @{@"imageviewForumAlert":imageviewForumAlert};
                    NSArray *constraint_H = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-19-[imageviewForumAlert(12)]-19-|"
                                                                                    options:0
                                                                                    metrics:nil
                                                                                      views:viewsDictionary];

                    NSArray *constraint_V = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-19-[imageviewForumAlert(12)]-19-|"
                                                                                    options:0
                                                                                    metrics:nil
                                                                                      views:viewsDictionary];



                    [self.view addConstraints:constraint_H];
                    [self.view addConstraints:constraint_V];



                }else{
                    imageviewForumAlert.hidden = NO;

                }
                /**NSDictionary *dic = [response JSONValue];
                if((NSNull*)dic != [NSNull null]){

                    labelNewForumThreads.text = [NSString stringWithFormat:@"%d new threads...", dic.count];

                }**/

            }else{

                imageviewForumAlert.hidden = YES;



                labelNewForumThreads.text = [NSString stringWithFormat:@"%d new threads...", 0];
            }
            /**else{
                labelNewForumThreads.text = [NSString stringWithFormat:@"%d new threads...", 0];
            }**/



            [self recurseForumActivity]; //calls same function 

        });

    });
}

}

NOTE

Also when i run Xcode and Instruments at the same time, the memory usage shoots up, why is this?

This is what Xcode shows in its memory usage:

NOTE - EDIT

On average my memory usage now runs slow but goes up 300kb every 15 seconds

EDIT

I found where the memory usage is going up, it's at this call after i trial and error:

NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:&urlResponse error: &error];

How do i stop this from happening?