Can you take photos of the chickens currently sick? The ducks that died could be an unrelated problem or coincidence. Were they in the same pen?
If none of the chickens are "pets" you could just choose not to treat it and see which ones survive. Provide fresh water and feed daily and let them free range.
If none of the chickens are "pets" you could just choose not to treat it and see which ones survive. Provide fresh water and feed daily and let them free range.
