mademan

I am growing 15 seedlings of chronic from wws. They are 5 weeks old today. I have transplanted them 3 times into bigger containers. The last trans. was about week and 1/2 ago. I am using organic soil. They are about 5 to 7 inches in height. They are under 24 hour lighting from 2 400watt hps bulbs. The lights are a foot away from the plants. Also 2 fans blowing on each light set up. They are in I think 3 gal buckets. I water them every 3 to 4 days with tap water. I have used miracle grow the second week but stopped after the first time because I heard it was not good for the plants. I have used dried blood meal last friday when I watered. I mixed into the soil. I also put worm casting into the soil last night when I watered again. I have pretty good vetalation with a industrial Air Mover. MY problems are that about 9 plants have turned or turning yellowish green. Some even lost the older leaves. About 3 plants are looking great. They have a huge amount of leaves. And very green. I am worried that the others will affect the nice plants. I know some plants veg. for longer than others. What is the veg. time for CHronic? Thanks for the time.