Lagging with multiple enemies

Hi there, In my game we are doing a wave survival (Not Zombies) but when we have like 7 enemies in game it lags like crazy, (It’s not my comp i have 8GB Ram, i5, gtx560) It seems to be when the colliders of each enemy are hitting each other it then lags like hell.

How can i fix this?

Unity’s CharacterController is really slow when many of them are colliding. I recommend using something else.