to deal with humidity, i set my AC to the "dry" setting (acts as a dehumidifier,) and i use a 45 Pint dehumidifier from best buy ($250 w/ a 4 year extended warranty) and this usually stays on the low setting (i set it on low and 60% humidity. it comes out a 39% right under the lights.)

also, HIDs usually make things dryer. i use flouros for veg cause its easier to keep the humidity up