we have game just about to be finished and we experienced this issue. We updated iOS on our devices to 5.1.1. and fps dropped from 60 to 40 on iPhone 4 and iPhone 3GS. We had 60 fps on both and still have more then 60 fps on android of our build. There were no code changes before update.
I did check for memory leaks, because new update fixed some memory issues and we have all clean and stable.
For me it looks like there is cap for fps in new release? Did anyone experienced this and know what to do to go back to 60 fps?
Thank you for any advice!