my advice . get rid of that cool tube get a flat hood like a ( raptor ) you will be much better coverage . that cool tube sucks . I used to have 7 of those .
http://www.amazon.com/Raptor-Reflector-Flange-Unit-Separately/dp/B009B1HNOA/ref=sr_1_3?ie=UTF8&qid=1398696612&sr=8-3&keywords=raptor hood
this investment is 200 but well worth it. its up to you . they will grow with the cool tube. your wasting a lot of light with it . this hood will drop the light right onto the plants