Just in front of the chicken hut you have to make a sheltered chicken walk surrounded by wire fences. You should place some of the wires under the soil and protect the edges with large stones. You can use nylon mesh or mesh for airborne hazards.
Stir the apple cider vinegar into the water very little and give it through the mouth of the chicken. Keep the animal in a warm place. I hope he gets better.
I think it's a herd predator attacking your chickens. First possibility wolf pack second possibility coyote pack. If you live in the wild, buy strong dogs on your land. Keep at least 4 dogs.
Geri