Final update: he passed away last night. It was just too cold for him to handle and the pain was too much.
I’ve been having fears that the Layena I use may have an impact on their health, since the same duck had cancer and died back in October. They used to be healthy ducks, and it could just be age, but nothing I’ve read has ever brought me to cancer.
I just hope he rests well at least, he gets to be with his brother