dwc blue dream, gdp, purple kush

1st ever grow, with blue dream, gdp, purple kush. using growlab 80 and 4 1/2 week flowering. 400w hps air cooled reflector. doing hydro dwc with 3gal buckets. 6" exhaust 4" intake. have 2 4" air stones in each bucket and also have a power head in each bucket for extra water flow and oxygen. using gh nutes for blue dreams and gdp, and for purple kush using advanced nutrients. blue dream grow hella quick and it's my tallest. stands little over 2ft. gdp is next smallest, and purple kush is the smallest plant and stand 12" high. so far had no issue with 1st ever medical grow untill now. starting to notice powdery mildew on leaves. since i have 3 different size plants i had to get some wood and stack it so it can be somewhat even.