I have a chicken that had a bald spot high on her chest. I isolated her and dusted her with DE. She continued to lose feathers, now around her neck and some loss on her belly. Redusted her with DE. She does not like being alone, seems to miss her buddies and is stressed just by being in isolation. I have dusted her egg box, put sand and DE so she can dust herself, but I do not see any improvements. She and all my adult chickens also have a cough, sneeze, I have never had this issue before. We were having a problem with a massive amount of pigeons in our yard. I normally let the girls free range during the day. All the other chickens are alert, active, eating and drinking well despite the sneeze. This one in isolation is eating and drinking well and laying normally, except with eggshells that feel like fine sandpaper. Also before I noticed the bald spot on her, I found an shell-less egg. Any suggestions as what might be the issue and are her sandpaper eggs safe to eat?