We have a 2 month old muscovy house pet we hatched ourselves. She is sweet as can be. Loves to be held; comes outside with us and stays close when we sit on the grass. If we get up and move away, she follows. When it's time to go back in the house, she happily follows along and in the door BUT...
Try a splash of apple cider in the drinking water every day. We had success treating a cough of one Muscovy. Not for A duck with discharge from nostrils or eyes.
We had success with 1 Muscovy who was coughing. Added a splash of apple cider to drinking water and it cleared up. We always add a little to drinking water now.