I noticed a couple days ago that my 6 Pekin ducklings were sneezing. It wasn't constant, and there was no discharge or any other syptoms, so I figured they were fine. Today, my biggest duckling's breathing is very loud. It isn't necessarily wheezing, but it sounds like he is breathing heavily, like you can hear each breath coming from his nostrils. He is the only one I am noticing this behavior in. What could be the matter?