I don't see any broken feathers and that is a very small patch of featherless chicken hide. I am going to advise you to read up on Depluming or Feather Mites. Don't waste your time looking for these mites they are very small and live and reproduce INSIDE the feather shaft so they are quite invisible to the naked eye and most dusts like Sevin 5% and DE are worst than useless..
Don't confuse feather mites with chicken lice, they are totally different. Good luck. You may need it. Dipping all your chickens at once is the way to go. Some of the pour on flea medicines may work just as well.