What strain is it?
Could be just the strain.
Certainly aint going to get much bigger in size at this point.
I assume you've flowered with these light before?
I remember something about you having cold temps.. what are your average day/night temps?
I Grow 4 Strains only 1 are a Cookies the Rest is Ice cream punch. For me they are behindI think it's a mix of things. Lower yielding strain, too much defoliation, and possible environment. Skip the cookies next time and get a better yielding strain.
Plant size and bud size is also a function of root development and root ball size. Not sure how long you vegged them but I'm thinking this is all about a short veg period and not letting the plants develop into larger plants early on.
What is the grow medium and how big is the root space?
Only 1 are a Cookie Rest are Ice Cream PunchProbably the cookies. They make small hard nuggets. Easy to trim!