12 Plants 8 CFLS - Awesome except 1! Help?

I have ~12 plants that are about 8-10 inches high that are about 6 weeks old, they're supposed to be M39, which everyone tells me that those plants are never bushy, jsut really tall.
Well theyve been doing great and i've never seen such bushy plants, ever. I've been slighty defoliateing, else are not getting light at all inside the plant.

There is one plant that some leaves are getting "droopy" I water once every 2-4 days ( 2 times a week) and give nutes once a week, there is no nute burn the plant is super green but the newer branches are very soft. Im letting it dry up to make sure, but i never water unless the dirt is dry. I gave about 1/2 strength nutes.
PH is at 6.5 and I test it daily.

There are about 3-4 CFL's ( 40 watt ) *Getting some 200 watt CFLs soon!* close to it. and there is a fan blowing on them
Temp is ~ 75F But I know the lights are close and giving off some heat, but the plants arent burned and if i put my hand it feels comfortable!

The plant is still in a relatively small pot, the soil is pretty clumped so carefull took the whole thing out to look at the roots without touching, theres a ton of roots at the bottom just asking for more space, I know I need to re-pot but I wanna make sure this is the problem, as if its not, I dont want to stress by repotting.
The other thing im thinking although im 90% sure its not it, is that the plants are already giving off a huge smell, so I put an air purifier with a hepa filter in it could that be a cause?

I will definately have some pictures in the morning. Thanks!