Wondering Why ?

[op8man]

I currently have a good grow going and am using some tubs with sprayers and bubblers. Then I have some DWC buckets going. All seeds are running along good. I am seeing good daily growth. My question is.......I have a deformity problem in the sprayer tubs and color. Half of them seem light green to me and some of the lower leaves have curling downward deformities. My PPM is good at 500-600 (thats where I like to run it. The DWC buckets have the exact mixture and those plants are dark green and healthier. DWC bucket runs all the time and sprayers run every couple of hours. Its not PH that is 5.8-6. My water has been tested good for hardness and other items. My PPM straight from tap is 100. Now I would think it is over watering. How come you can run a DWC bucket all the time and achieve such results and water the tubs less and have this going on ? Is it something else ? The whole plant is same color.....a lite green. I would think it was interstrain natural coloring and variation if it were not for the wilting. No dying or burn showing yet. What do you all think. I will post photos soon.