Small flock, four free range 1-yr-old Black Australorp hens. Diet: Corn scratch, Purina Layena, freeze-dried mealworms (winter-not many bugs out), oyster shell. Our leftovers for treats, usually veggies, fruits, pastas, cheese, bread. The hens are laying good eggs and we avg about 3 per day between all four. Shells not weak, size is good for their age, nice yellow yolks. Problem: Skinny. Breast bones very prominent. Also, all the birds seem to be losing feathers - particularly tail feathers as they only have a few feathers left of the nice plumage and most of their butt area is the fluffy "under" feathers. Green sheen is still nice and they are not losing from any other area. Even more strange is more feathers are missing on the LEFT side of their rears - on all 4 birds. (???) I thought it was possibly placement of the heat lamp in their coop.... but then again none of the feathers seem "burned" off. The birds are eating well. One actually is being very broody right now, not sure why but it sits in the coop all day hogging the nesting box. This particular bird's crop was full and soft - possibly water. All the other birds have full crops that feel seedy (probably due to seeds/scratch and pellets) and I will check again in the morning to make sure they are not impacted. All birds are defecating normally with normal stool. Any ideas? All of them, except the broody one, are still alert and active, laying, eating, drinking..... why are they so skinny and losing feathers?