I start all seedlings in 1 gallon pots and put them under 160 watts of Fluros and when they reach 14" in height I re-potted them into 5 gallon buckets and moved them under a 400 watt HPS.
My Soil mix - I use Black Gold Coco mix as a base and add 1/3 cup of blood meal and 1/3 cup of bone meal. 2 tablespoons of Dolomite lime.
That's it. If during flowering I start to see any yellowing I have been adding some bat guano mixed into their watering.