Help! I have a chicken that had a sudden onset of respiratory distress. She is stretching her neck out to breath and occasionally gasps. She is very lethargic and docile right now. None of our other birds are showing any signs of distress, but if it is contagious I want to stop it if we can. They are housed in a coop with very good ventilation. There is no visible discharge nor foul smell. She does seem to have some white substance on the feathers on the underside of her neck, but it is dry, not wet or smelly. My kids think she may have eaten something and is choking on it, but I don't know if that is possible. Any ideas? Thanks!