With that cool tube I could get it 6 inches from plants if the room is A/C and 2 or 3 good fans blowing right across the topps of your plants. Get a few fans like small oscilating ones to blow back and forth.

Without fans your cool tube is getting tooo hot that's why the light green burn on closet ones. A light with no cooltube could be raised up almost a foot higher.

OH and awsome buds there man.