I'm new to this, but it would seem to me that if things aren't working, you should try something else. So maybe try a fewer colliders?
(please vote my question yes because it won't let me ask my question until I get more than 10 points EDIT: You also might try using a fixed frame rate, like described here: - somethinghttp://obviam.net/index.php/the-android-game-loop/ Maybe you can fix the framerate so it stays high
EDIT2: Maybe you have a memory leak? This article talks about hyperlinks and images and such)that possibility on iOS: http://www.cocos2d-iphone.org/forum/topic/6641