Can't wait to see this game finished
I stugled with this game for about 5 minutes then I read your description. I like the game and you're an awsome designer, so here's what you have to do at a first look.
1) Make sure every animation has a startMe() and stopMe() function. All your animations are probably running on the background at the same time so you need to start them only when they are visible, and stop them when they are not visible.
2) Remove any eventListeners the are not used anymore, also remove from the stage all the leaves that fall of the screen.
A little animation managment is all you need
Hope this helps and can't wait to see this game finished ;)