The slow growth is due to your heavy defoliation of these little plants.
Less leaves = less energy being made = less growth.
Giving a product with humic acid, fulvic acid or amino acids (or all three for best results!) will get your plants moving and like RunWithIt said, adding mychorrizae will really help and I will second what he recommended, "Mykos" by Xtreme Gardening is excellent! Have been using it for a while now and can't say I would ever grow again without it, the difference it made to my grow and without changing anything else, was noticeable to the "wow factor".
Hope this helps,...........
Organoman.