I think you are definitely going to want more air stones, and make sure you have plenty of air moving through them, ie. nothing less than an industrial sized air pump, no Wal Mart fishtank air pumps, etc. You really need to churn the water in bins that big to avoid stagnant areas and rotten roots as a result of the stagnation. As for nutes, not so sure on GH Flora because I use organics. As for the number of plants per bulb, I've found it much easier to grow one big one under one bulb. Good luck!
The above post is fictional and should in no way be taken as truth.
If I were to grow cannabis, I would only do so to supply myself and my close friends. Doing this would take myself and my friends out of harms way by knowing the source of our cannabis, as well as take hundreds of thousands of dollars off the black market annually. It would also lower the demand of black market cannabis, and would ultimately help keep cannabis out of the hands of minors.