So one of my chickens has developed a bald patch on her chest. I have checked her over and visually I cannot see any parasites. She seems healthy and lives with her 3 sisters. A couple of the others look a little rough on the chest too but not bald like her. There doesn't appear to be any bullying or pecking by the others, they all seem to get on well. Any ideas? I can of course take her to the vets but wanted to ask here before stressing her out with a vet visit.