iphone - iOS Development: What are some ways I can troubleshoot a lag issue in my game that occurs 15 - 30 minutes after playing it? -

i'm building ios puzzle game become familiar platform , few of testers noticing severe lag issue occurs intermittently 15 30 minutes after playing , lag doesn't appear associated specific part of game. i've tested app using leaks instrument , havent found leaks yet.

1. what things cause game instantly begin lag after playing while?
2. what methods/tools use troubleshoot lag?

thanks wisdom!

update: new ios developer, under impression leaks instrument report @ least of memory leaks, comfortable believing app managing memory when no leaks reported. not case! after following few of suggestions posted here, watched few videos on how use allocations instrument , found app losing ton of memory on time and, after spending 2 hours walking through code , fixing memory-related code, game no longer lagging or reporting lost memory or memory leaks. thanks, all!

the main thing memory warning, in turn cause bunch of game assets possibly freed @ once...

instead of leaks, place start objectalloc tool. leaks shows memory used application knows about. objectalloc shows total memory used, , real issue seeing graph of memory used climb on time.

lastly, try game state while using timeprofiler instrument, see kinds of operations took lot of time when game slowed down. have on device, not tell going on using simulator.