How is your Mallard today? looks like Amiga gave good advise here is the link about Toxins and what to do
https://www.backyardchickens.com/threads/flushes-for-aiding-in-toxin-removal.700526/
https://www.backyardchickens.com/threads/flushes-for-aiding-in-toxin-removal.700526/