My yr old hens are missing feathers, on breast, back, vent and one neck; for about 2 months. Some of the spots are very red and a couple have scabs. I didn't see any mites/lice but feathers on back looked scraggly so I treated them and the coop/run with Poultry Dust on hens and Sevin dust in coop/run 10 days ago. I retreated hens yesterday with Adams flea and tick spray. They do not free range but run is 10 sq ft per bird and coop is 4 sq ft per bird, the entire thing is under roof. Egg laying hasn't slowed down and I feed them 16% layer pellets and throw in lg cup of scratch every few days unless its hot outside. They have grit, there's no rooster. I gave them Vit and Electrolytes 10 days ago and I'm worming them now because they seem skinny, also give them lil yogurt every 1-2 wks. Feathers not lookin any better. Thanks for any suggestions or advice.