Top of plants not budding (pics)

My plants are due for harvesting in around 3 weeks, and the buds on the lower branches are coming along just as they should. The top cola on 3 of the 6 plants are just fine but on the other 3 they aren't growing, just creating some shitty cabbagey looking leaves. Anyone got an idea?

There getting fried...move them away from the light.

That bud comes out hard and crusty, not a pretty
sight.

I would assume that they are predominately sativa? I see you are from across the pond so to speak. Your plants look either of two things. They are very sativa'ish or they are they are fox tailing because of extreme heat. If they are three weeks into flowering they might have stopped the stretch and are going to fill out. If the tops contonue to not fill snap them in half and tie them back to themselves.Good luck!

i woul prune some of that shit, focus all energy on cola, just from what i heard

Thanks for the advice so far, i'm going to bump this, any fresh ideas would be appreciated!