That might be it one my hens was hurt my dog before but I'm not which hen laid the eggThis can be very normal in a new layer, and can sometimes occur in all hens. If it occurs repeatedly, there can be a problem with the hen’s shell gland. I would make sure that the hen is getting a layer feed that has more calcium, and supplement with crushed oyster shell in a separate container. My hens prefer crushed egg shells fed back to them. Viruses, such as infectious bronchitis, can cause egg shell problems, and I even had a hen who was injured by a dog, who never laid a normal hard shell the rest of her life.