I’m so sorry to hear about your pretty bird

My sincerest condolences. I just wanted to add to this, bc it really is hard to find info on this for poultry, most of the info is related to smaller birds, but my hen has had really strange symptoms off and on for awhile. It wasn’t until recently she developed strange but subtle throat/ ear symptoms, then raging diarrhea. Long story short, I’m pretty sure this weird culmination of symptoms is air sack mites. A vet can check from a swab test (I’ve read). I wonder how many ppl w birds w mysterious throat or sinus or breathing issues are really dealing w these throat mites. I was really worried about losing my girl, a vet dosed her w Ivermectin, 30 minutes later she was trying to dislodge her throat, then she was back to herself again, then next morning severe diarrhea, gone. It was really incredible. I plan to continue an Ivermectin treatment. She had tested negative for parasites & had been treated for gape worm prior to this.
Again, so sorry about your duckie. I hope this info helps someone.