problems with chickens loosing feathers

[deerladysmom]

My hen has lost all the feathers around her vent. She is one of four hens, no roosters. THe others are not experiencing this problem. CAn not find lice or mites, have thoroughly cleaned the coop and am using wood ash in the ranging area. Her skin is very reddened and looks sore. Any suggestions what might be causing this. Other than that she is healthy, laying well, eating and drinking and socializing with the others as normal.

 

[WildfireSmitty]

how does her comb and wattle look? pale? swollen?
same age as the other hens? or was she introduced after?

 

[deerladysmom]

Her wattle and comb look good, full and good color. She is the oldest of the chickens but the red sexlink with her is the same age and the 2 others are one and a half years younger. THe other chickens are not demonstrating any problems. She is also laying regularly and seems active as usual.