Why is PvZ 2 Stuck on 30FPS ??

I just downloaded PvZ 2 again ( Last time I played was a year ago but then I took a break for some time ) Now on my new phone which I recently got.  And the game just seems to be stuck on 30FPS . The experience doesn't seem to be much different than my old phone which was a really old budget phone so lag was normal on it and I was used it it . But now on my new phone which is a really powerful phone it seems to be stuck on 30FPS.  I don't understand if the game itself is like that or it is a big or something .