Lil question bout air flow

How much ventilation would a 4x2x10 closet grow with 4 plants need? Ive got a standing fan going already blowing on the plants and the door is always slightly open. I am wondering if I am going to need to purchase any exhaust pumps or anything like that. Also, I am using worm castings for fert., will this be enough to sustain the entire grow? Would it be a good or bad idea to mix chemical fertilizer with organics?
i will be using 400w mh and 400 w hps

I think the fan should be good. Maybe get one more in there to be safe. for nutes, get some blood/bone meal. wait for some other more experienced growers to reply, dont just listen to me. hope i was able to help a little, goodluck with your grow

alright ill put a couple fans in ther and add some blood meal to the soil.