I have a flock of 20 Buff Orpingtons. 19 hens and 1 rooster. 5 or 6 of them have developed these sores, all on the same locations, on their backs. I have not observed any fighting or obvious issues among them and I cannot see and bugs/mites in the affected areas. Does anyone know what this may be and/or have a solution to it? Thank you to anyone who can provide insight.