Hello all. I have two australorps that are 3 years old loosing feathers around their butt, vent and up around their tail feathers. Just on the back side nothing under the wings or middle to upper back. One has some feathers missing on her head about a pea or a little larger area. No other areas are loosing feathers, they seem to be eating. I picked up one to look for bugs and could not see any. I put some poultry dust on them on Sunday. I run no rooster. All other chickens seem to be ok. Are these going through a molt? Suggestions?