I believe you've said you offer your chickens chick grit, for baby chicks. A couple of people have recommrnded regular poultry grit, which is coarser, for adult chickens. If you have offered your chickens that, I have not seen where you've said you've offered that. Once they're adults, they won't eat the baby grade grit. They need the adult grit. Also, it's really hard to tell if they're actually taking grit, as the level of grit in the dish goes down exceedingly slowly. If you are using adult, coarse grit, I would not assume they are not taking it. Keep it available. They'll take what they need.