Have you changed your flock population since this post?All my girls get 18% layer pellets and free choice oyster shell and grit. They do get scraps occasionally and scratch on cold nights. I put 1 Tbs ACV to 1 gallon of water. I have 8 birds (5 are bantam) in a 6x4 coop with ample roosting space, 4 nest boxes and their run is 20x14.
Could be a crowding issue.
Diet sounds pretty good.
I'd cut out the ACV for a few weeks, IIRC it can inhibit calcium uptake.
OK to give once in awhile but not needed constantly....and it's one thing to change see if it helps.