When you get to flower running your exhaust when the light is out is a good idea to keep humidity down to keep mold at bay with dense flowers growing. Plus accumulated heat at night in the canopy can make your buds airy. Just some stuff to consider bro, you can always get a fan speed controller and run it at lower speeds when the light is not on, that's what I do. Along with an osc fan and a little 9in high velocity fan like you used to have below your pots, keeps my girls plenty happy at night. A small digital thermo/hygro from home depot or such for $10 that keeps track of your humidity and temp hi/lo can tell you what's going on at night and save you alot of headaches...Your B.O.G.'s leafs are starting to fill in a little and look more like mine, but still look a little more sativa dom than mine. I love the SATIVA'S. Take it easy bro, Peace out.