Plants are lookin good! how long did you veg them? I'm using a 600w for flower and about 6cfl's for veg under a bubble cloner. It's working great, as the plants have a lot of roots compared to leaf development. I think the key is to have a high airflow air pump. Mine flows 70 liters per min through 6 air stones in a 2gallon rez. I'm going to put them into a drip system later so i'll let you know what i find about root development. I have a nutrient mix called root66 thats suppose to promote root growth. Are you using any nutrients in the mix and whats you're ph at? I'm running 6.8 on my clones but plan to bring it down soon.