I vegged for 7 weeks,you can take about 1.5 weeks off of that,she stunted her growth twice. 1st was because of fungus gnats at week 3 of seedling 2nd was because i topped and fim'ed her. I only noticed the topping that stunted her growth though. even bag seeds can be good, atleast all the bag seeds I've tried out here in hawaii, you just wont know untill you try it.
I am still learning much, but if you can actually get that 600w hps in there without stressing the plant by light,heat and giving very good ventilation, id say your in for a good learn and grow process. You've got the lighting to have a good yield, keep them thriving, healthy, dont overdue your nutes(do not over water) and check your water quite oftenly with that much light in a 3 square feet. Its not about learning what you need to grow, its more or less what the plant wants and needs to grow. My first grow loved nitrogen, i could feed at high ppm levels and not have any stress, my current grow will stress out at even half reccomended doses of nutes in the same soil and pot. Right now, your most important factor is ventilation and the way you aim your light for that 600w hps because im not so sure if your height will even allow 600watts of gas over a plant. If it doesn't, you will just have to figure out a way to diffuse some light away, assuming you want to stick with that space and light.