A couple of other things I noticed. You have flushed them 3 times in 7 days, they could be just showing signs of overwatering. Also... Measuring outgoing PH and EC in coco is not worth doing afaik. Because PH and EC readings are affected by small particles in the coco. You just have to measure what you put in.

I think I can see 7 plants in one of the pictures. 1x250w CFL will not produce enough light to grow 7 plants. You wil just get lots of small popcorn buds all over the plants, instead of fat buds.

hope this helps...