This puts a new spin on things, if the soil you're using is the Miracle Grow that is supposed to retain moisture, I transplanted a 4 foot 6 inch plant into that soil last year, and it stopped growing and wasn't worth smoking at harvest time. Not sure that is definitely your problem, but I'd be suspicious of it. With adequate nutrients and 600 watts of light, she should be quite a bit bigger already, and have some bottom branches started. If you'd like to know one of the best soils I've ever used, try Masters' Pride Professional Potting Soil. Not many people are hep to it yet, and it isn't found in many 'grow stores', but lots of regular nurseries carry it. It has all the guanos, chicken manure, and other organic nutrient sources, and it already has Mycorrhizae in it. As soon as you open the bag and get the smell of it, you know it's good. I used to use Fox Farms Ocean Forrest, but this is far better. Just don't buy a bag from the top of a pallet that has been sitting in the sun. I grew plants to 3 1/2 feet with it, before they needed any further ferts.