I've determined that one of my chickens has sour crop, but I can't figure out who. I can smell that sour milk smell, but none of them are acting sick. I narrowed it down to 2 of the silver laced wyandottes, but neither of them smell like anything but a normal smelly chicken. Felt all their crops, too, and didn't notice anything unusual. So then I smelled the other 8 (and got a nice scratch on the face for my trouble!), and had the same issue. I know the problem was caused by lack of grit because there has been about a foot of snow on the ground for the past week or so, so they haven't been able to dig up their usual rocks & stuff. So my question is, should I go ahead & put out the plain yogurt & apple cider vinegar for all of them? I know you're supposed to massage the crop & restrict food, but I don't know which one it is to give that treatment to. These chickens are not pets, but I don't want any of them to be suffering.