Feed everyone all flock and provide oyster shell on the side.
Valbzen goat wormer is a good wormer.
https://www.backyardchickens.com/articles/valbazen-albendazole-doses-for-poultry-waterfowl-and-game-birds.75490/
What protein is the layer? Roosters and non laying birds really shouldn't have layer, it has too much calcium.
D.e doesn't work as a wormer, it doesn't do anything in damp or wet environments, which that's what the inside of animals are.
It could be depluming mites or diet.