What is your general location? It could be fowl pox by the looks of it. It is odd there are no scabs forming on the comb. If it is pox, there is no treatment. Some will paint Betadine 10% on the scabs to help dry them up. It lasts about 3 weeks, and most grown chickens recover, unless wet pox is found. Wet pox causes yellow lesions inside the beak and throat. Chicks may have a harder time fighting either type of fowl pox.