ya 400w same here, in a closet I cut to holes in my door though one at bottom for little fan blowing in and one at the top for hot air to be pushed out...shield them both, in 12/12 you dont want no light comming in ...sexing them will take with in 2 weeks of 12/12. 90 degrees wont kill your plants but over 2 hours at like 100 will. You should have a fan blowing on the plants, that would help even if the ambiant temp is 90. Plus they wont be so week when trying to bud...lol Does that plastic bin have any holes in the bottom? Hope so ...it would help a lot later on in the plant life . What is the PH of your growing medium? It could keep changing if you water with any thing other than just plain water if you have no holes in the bottom. Oh and if you rig a fan on a timer make sure it comes on right when or even befors the bulbs come on, you will gain 3-5 cooler degrees this way ...It doesnt let the bulb get hot to even raise the ambiant temp as much....peace