Like the other guys have said you need to sort out your air circulation. But there's a couple of things i've done to help reduce temps a little. First off change the hours when your lights are on to the night time, say 8pm-8am assuming ur in flowering. (When it's already hot with the sun in the daytime you don't wanna be adding heat with your lights too) I'd say 600 watt is a bit too high for 3 x 3 area, change down to a 400, at least while you have heat probs. The last suggestion depends where your grow is, mine was in a bedroom and above as you'd expect was a loft, covered in insulation, you got it, take up the insulation above where your grow is. Good luck!