The EE you are looking at has fluffy feathers on her head. It is not a scab. The rooster has that mark because of an old injury, healing. I can assumer you none of those marks are unknown scabs. Dont mean to argue, just want to point it out.These dark areas on the comb. With one being a scab. You can also see where the chickens are pooping on the ones below.
They are sitting on the bedding.