Lately, one or more of my chickens have been laying eggs at night. At first, I let it slide, because I figured it was just them getting used to laying again after molting, but I have been finding one almost every day when I go to let them out in the morning. In, the beginning, we just thought that it had been pushed out of the nest because sometimes they are on the floor, but mostly we find them directly under where they roost all the way across the coop. Some have very little shell while others would have probably been fine if they had been laid in the nest. I have tried feeding oyster shells, but that hasn't done much. Is something wrong with my hens?