8 wks of veg they should be monsters, I think you have watered a little to often right from the start, by drying them out to the point of wilt you can find the sweet spot to feed they like a wet to dry cycle, sometime when you transplant a small clone or seedling into a large pot and its kept too wet it smothers the seedling and as the coco drys from the top it draws from the plant, the response is transplant shock and nutrient lock out they just get set back, they can bounce back healthy but lazy.
You can minimize transplant shock to virtually none by having the same environment conditions and keep the media not wet, feed a very weak nut strength and build roots, when have the foundation down below they will explode, if you slow them down early by hampering the roots they just plod along like fat cats.
Cheers