I have a setup very simular to yours and I would transplant those to bigger pots I use 5 galon buckets, and set the plant in up to the top leaving only a couple inches from the top. 3 galon pot setting down in you only have 2 galons of use. look and see if roots are stuffed in the water vent holes in the bottom of the pot. With co2 I bump my ferts untill I burn the tips then back off a little its hard to way over feed with co2. When you transplant to bigger pots I would flush those and start ferts over. with soil up at the top of your pots and useing the full pot your stalk will fatten up and your secondary branches will carry the weight much better. Useing full pots just makes you water a little slower my last harvest got root bound and got cut 5 days early witch didn't hurt but showed me to fill my pots all the way,was useing 3 gallon of a 5 gallon pot.