Before I update Xcode version 6.4 it still work fine.
here is my code
NSMutableArray *result = [[NSMutableArray alloc] init];
NSString *path = @"http://rmfl.nagasoftware.com/api/plant_by_season.php?lang_code=1&season_id=0";
NSURL *json = [NSURL URLWithString:path]; // jsonString
NSLog(@"URL is %@",[json absoluteString]);
NSData *jsonData = [NSData dataWithContentsOfURL:json];
I suspect you also updated to iOS 9, if so that is the problem.
The solution is to up date the server to https TLS 1.2 and forward security.
Another solution is to whitelist the url on the app plist or even if necessary allow all http connections. This reduces the connection security, the best approach is to update the server.