Good point about the possible skin allergy, Chris. I think this thread has identified three possible lines of diagnosis - feather pecking, (addressed by beak bits) environment in the run and coop, (as in Chris's enquiry) and feeding.
The hen in the pic looks like an ordinary brown high-performance egg laying hybrid, the kind you'd find on commercial farms, like the ones that get rehomed as exbatts. Are they all the same, Dye, and from the same supplier at the same time? If so, possibly genetics and nutrition may have something to do with it. Fast-track hybrids are bred to produce eggs, eggs and more eggs, and feather condition is probably a relatively minor factor, given the conditions factory farmed hens have to live in. They definitely need a high-performance food to cope with both egg laying and feather maintenance, out of doors in winter.
I think that, whatever you are feeding them, it would be an idea to change to one of the leading brands recommended previously in this thread, in case the pellets you're using contain something they are reacting to, or are not giving them the full range of nourishment they need. I'm not saying that what you're giving them is inadequate, just that a change to a top-quality brand would rule out allergies or deficiencies. This may be more important than adding supplements, which may not be what is needed.
Then, if they're perching OK off the floor at night, and as you say, you keep them clean and they have relatively sheltered living conditions, and are clear of parasites, then maybe you will have all three bases covered!
The hen in the pic looks like an ordinary brown high-performance egg laying hybrid, the kind you'd find on commercial farms, like the ones that get rehomed as exbatts. Are they all the same, Dye, and from the same supplier at the same time? If so, possibly genetics and nutrition may have something to do with it. Fast-track hybrids are bred to produce eggs, eggs and more eggs, and feather condition is probably a relatively minor factor, given the conditions factory farmed hens have to live in. They definitely need a high-performance food to cope with both egg laying and feather maintenance, out of doors in winter.
I think that, whatever you are feeding them, it would be an idea to change to one of the leading brands recommended previously in this thread, in case the pellets you're using contain something they are reacting to, or are not giving them the full range of nourishment they need. I'm not saying that what you're giving them is inadequate, just that a change to a top-quality brand would rule out allergies or deficiencies. This may be more important than adding supplements, which may not be what is needed.
Then, if they're perching OK off the floor at night, and as you say, you keep them clean and they have relatively sheltered living conditions, and are clear of parasites, then maybe you will have all three bases covered!