yeah that's more bad genetics than growing environment...not much you can do. Never heard of Pit Bull man...you should try a really stable strain from one of the bigger seed banks...like super skunk from Sensi or WW from Greenhouse. I'm getting both next time I order up seeds.
I have the same problem with these plants...I didn't LST them and I didn't put the HPS right on top of them and they stretched but all the leaves below the top 10% of the plant just yellowed and fell off with just brushing against them. I'm pretty sure it's a nute issue, because I didn't use any nutes at all. On the plus side the bigger one I've got going smells SO fruity...and the cola is TIGHT...I remember the bag I got it from...the bud was just like it...perfect and tight. If I had grown this right I would've gotten a lot more. Not sure if you can see but the leaves are like RED now. Next time I'll LST and bring the lights down to the canopy and get it right but this grow was kind of an expirement and it went horribly wrong. Waiting to smoke this crap.