Several of my chickens, and in several months, have been afflicted with bare skin on their necks. It doesn’t appear on other parts of their bodies, nor is it limited to either sex. The outer layer of the skin thickens and turns bright orange. After some time it can be removed without hurting. It takes an extremely long time - several months- before it heals and new feathers come out. It doesn’t effect the rest of the flock, only one or two here and there. I keep them separate from everyone else. They’ve all been vaccinated for Marek’s, though this condition is not symptomatic of the disease. I’m clueless here.