PixelPower, I was already following many of your advices but I'll be sure to check again all of your guidelines
tunepunk i had no particles, three text objects and many objects with the Tint effect.
I had about 50 sprites with a permanent Tint effect applied (an event trigger once to activate the effect), I used this trick to color some white sprites with 4 different colours, one for each player (yes I'd like to support up to 4 players), these sprites feature the players itself, their health bar, input device, input feedback and some other player-related objects like a crosshair.
After removing all of these tint effects the game runs much better so i guess that was the issue.
Since i still need these sprites to appear of a different colour depending on which player they are related to should I use different animation sprites, one for each colour and play stopped animation with that fixed sprite?
Also, sprites like input device and input feedback are actually sprites with collision disabled but should I turn them to - for example - tilebackgrounds or tilemap in order to get better performances?
Just to clarify:
-Input devices are a series of sprites which represtents input devices and their layouts like touch, keyboard layout 0/1 and gamepad 0...3, these become opaque when that input device sends a command and trasparents otherwise.
-Input feedbacks are a series of sprites which tells when a certain player is giving a certain command such as "right direction" or "button A", they change their opacity accordingly.
Since they are normally all white i used tint to colour them as the player they were connected to.