I read your post and you mentioned Coccidiosis. If your chickens have Coccidiosis, you may want to start them on Corrid powder mixed in they're water. I would clean out the coops, wash down with bleach and dawn, and separate the sick from the healthy birds.
Corrid should be available at
Tractor supply or most feed stores.
Cocci is caused mostly from chickens scratching in unclean coops, coops with too much poop, or them pooping in their water supply, ext... Worms live in highly pooped areas, and the chickens eat these worm's that live in the poop, and then the chickens get this disease in the lining of the intestines. Sometime's you may see blood in their poop, and it will be runny. Under roost area's is one of the most highly contaminated area's that are often overlooked. Poop build up is not good for raising healthy chickens.
There is lot's of post on Cocci on this site that can tell more detail of this disease. Most birds with this will loose weight, stand by their self, stare into space, look sickly, are non active, and have runny poop. The comb and wattles will be pale, and over time they die from lost of weight and dehydration.
Replacing their water with pedialyte or gatorade mixed 50/50 with water, a lil sugar, and the corrid powder, This will help re-hydrate them. If they don't want to drink, you can use a feeder tube with the squeeze bulb like the ones used to give children liquid meds. This should be done at least 5 or 6 times a day, if they don't drink fluids or eat.
You can also mix yogert with a lil water or milk and feed them. This is a good addition to the other fluids, and will help re-gain weight.
Saving chickens that have lost most their weight will be a uphill battle. It can be done, but you will have to force feed them until they recover. It's like a dog with parvo, death is caused by dehydration, and lost of blood sugar levels.
Good Luck