Hey guys, thx for the help. But after I tested these solutions, I found out that the problem whas with the turret behavior. Turns out that when it was set to rotate, it would result in lag. I solve this problem by disabling the rotation, and creating custom firing events.
Before, with 20 towers and 20 enemies, I would get 30~40 fps, now eith 80 towers and 60 enemies I get nofps drop at all!
I`ll update this with the events later, i`m using a tablet and typing here is hard >_<
EDIT:
Alright, so, for everybody out there making heavy use of the turret behavior, this might come in handy
<img src="http://i.imgur.com/Ove6m.png" border="0" />
(the sub-events are no relevant)
Items are turrets, Enemies are targets