How much air circulation do you have in the grow tent itself? If you don't have any I would suggest this as your next course of action. The addition of fans dropped my grow room temps about 3 to 4 degrees above ambient room temps during lights on and about the same lower during lights off. Which means about 75-76 degrees for highs and 68-69 for lows.

You really need to get the air moving around inside the tent. Your plants will love you for it.