Your code is the most likely culprit.
I made a post(not a thread) about this a few days ago. Where I went over that C2 and CJS are fine at rendering. The problem was in my code. C2 doesn't optimize code and more especially it doesn't optimize Sheet ROOT events. The more root events you have occuring per tick the more your game will slow down. You will especially notice with older devices.
Also what surprised me was that even just having a GROUP or an included EVENT SHEET will impact performance there code calling also seems to slow down performance.
As a test set up the most complex scene in your game. Then detach your EventSheet from the layout. I bet anything your performance will jump to 55+ as long as you keep to mobile gfx standards.
I was surprised after reading this, I tested this in one of my games that have little slowdowns when i have a lot of objects in screen (140-160 objects), and 80% of the code is in functions, in another evensheet. I tried to move all the functions to the "game" evensheet, I removed the "Functions" evensheet and i have exactly the same performance.