I'm tested my game with Samsung Galaxy s2 and galaxy s3 via Cocoonjs by ludei, now i'm in the same trouble.
My game running good in galaxy S2 with fps range 55-66 all the time, but with galaxy S3, after testing a few minutes, the fps drop to 38-4x fps and i really don't know why... I think galaxy s3 with powerfull hardware than s2 can run even smoothly.
I'm tested 2 of my games, galaxy S2 work fine and game run on Galaxy S3 always drop FPS in a few minutes, from 6x to 4x. I try anythings i can to change my code and etc to fix the problem... But it's still happen. I'm about to release my game to google play.