Hi, so my about 5 weeks old Muscovy duckling has been breathing heavier than usual lately and sometimes with an open mouth. That’s really the only thing that has been different about him. He’s been eating his mazuri waterfowl diet food normally, drinking water, pooping, and acting normally. He lives with another duckling about a month older than him. We keep them inside for the most part but we do take them outside for hours a day. They have their own area of the house with an area with heating pads for if they get cold. When he was younger I did have to take him to the vet to get antibiotics for a respiratory infection they said he had. I had to take him to the vet a few days ago for other reasons but the vet did say that the lungs and heart sounded clear and his nostrils were clear. Anyone have any ideas of what could be making him breathe hard?