Are the hens moulting? Chickens moult and lose all their feathers once per year. They have a higher need for protein at that time as well so you can boost the protein level in their diet. Some treats like a little bandsaw dust, some mince, or anything high protein can help. Putting them on a vitamin supplement like Soluvet plus, or something similar from your produce store is a good idea if they are in moult as well.
If they are feather pecking, spraying something blue on the area can help. Chickens are attracted by blood, so the new feather quills breaking through the skin are attractive to them.
There's a very thorough thread about featherpecking here: viewtopic.php?t=8599
If you are not sure if that is the problem, then post some pictures for us. Also, go to the top of the Good Samaritan Section and copy and paste the Basic Checklist for the Sick bird into a post here and answer all of those questions.
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Feather Clubs Association of Qld