I would also use some type of mycorr. Like great white for example. After using this my root ball almost doubled.
after i root my clones and go to transplant i either sprinkle a dusting on the roots, or make a concentrate with it and soak them. Also try letting them get a bit bigger roots before you transplant, it made a world of a difference when i started out.
your stems should be getting very hard and low to the medium almost like a slight bark.
i also use a custom blend of fully organic living soil.
IMO you can't beat soil. Hardly ever fertilizer if you make your own soil, no ppm checking and all that, much better bud and for me at least the highest yielding. I used to do something very similar to you but a slightly longer veg time and would flower in 2 gallon equivalent air pot. I would yeild 25-35grams per plant