Poor performance on Windows Phone 8

Hi. I’m trying to port an android/iOS game to windows phone 8(cocos2dx v 2.2). I’m using the exact same code base that I’ve used for android and iOS. The game functions just fine, but I facing some major FPS drop. The game runs flawlessly at 60FPS in android and iOS, but I’m getting roughly about 35FPS on wp8. Has this got to do anything with differences in OpenGL and directX?

I doubt its got to do with the game’s logic and calculations because when the game starts in windows phone, it starts with 60FPS on the main menu, which has got like 5 sprites. But as I add more sprites on the screen, say about 30 of them(average number of sprites when I’m IN the game) the FPS rapidly drops to 35-40 range. Note that there are no schedulers or update functions running at this point. I did the same test on Android, but the FPS didn’t drop. Does the win8 port of cocos2dx suck?

Any help,comments or redirection to useful articles would be appreciated.
Thank you.