One of my 5 hens started losing feathers on her wings at about 6 months old. The feather loss progressed to her back, and then her vent. Here it is 6 months later ( she's almost a year old), and she's completely bald on her back, vent, and wings. Sometimes it seems she's getting a light layer of down growing back, but then it's gone; that's why I put a saddle on her( by the way she never started laying). Now 2 of my hens are bald on their backs, and my other two are starting to lose feathers in the same spot. We have checked for mites and lice, and have always treated their coops and yard with DE. Could they be molting or is it something else?