Bibb growing loose heads

[Gnomegrown]

Hello all Newb here,
I have a good size vertical setup in my garage, (DWC, 2.5" deep), using led, Co2, O3 injection, a/c at 68 degrees water at 66 degrees, 75% humidity using chem-grow 8-15-36 mixed per instructions.

PH is a 6.2 with little fluctuation and nuts are at 650+250 source water.

I cant for the life of me get a tight head of Bibb, the leaves are long with a loosely formed head.

Any ideas on what to do? My oakleaf is doing great, bibb is just taking too long to form a dense core.