The leaf item should be fixed now.
I've noticed the slow down on my android phone before as well. There was an update a while ago to try and resolve it and the latest update should be better performance wise. But it's clearly still an issue on some devices and might still be there. It's likely a memory leak, which is a pain to track down.
If you don't mind, can I ask what android phone you have and roughly how many battles you can get through before the slowdown. Hopefully I'll get a better look into what's going in the next few days.