They were in flight cage with 4 other Gouldians and they had begun to incubate constantly - mostly the hen but he mostly stayed in the nest as well. For two days, they only came out a few times quickly to grab a quick bite and drink then back into the nest (hatching wasn't due for another week). We had just finished a two full-day treatment for air sac mites (March 15-17) using Moxidectin in their water.
Yesterday she came out, landed on the cage floor and began to gasp for breath. She would act like she was coughing but no sound ... just these jerking motions and furiously rubbing her face and beak.
I put her in hospital cage with heat and millet but she died before we could review our 50 pages of notes on what to do - within 2 hours.

We've been trying to figure what is wrong and now today, HE is rubbing his beak, eating constantly, and acting like he is choking!! We think it is something contagious and are researching but remain puzzled. It looks like air sac mites and scaly mites but they were just treated (reviewing videos from those two days, he drank 4 times on the 15th and 3 times on the 16th and his poop looks like milk. He looks 'swollen'. His feathers aren't fluffed but his chest is puffed out and he is sleeping mid-day.
He is jerky-coughing violently and rubbing his beak! He still has a lot of energy and it will be a huge task to catch him. Whatever it is, if it is contagious maybe best to leave him there and treat the entire cage?
Medications we have: Amphotericin-B, Baycox, Matrix, Moxidectin and Ronivet 12%.