We recently acquired 4 Muscovy ducks to keep our back runner duck company. We have noticed that one of them sits a lot. She doesnt appear to be in pain but it is like she cannot stand for long. She waddles around with the reset of the ducks but every time they all stop she sits down. When the rest of them decide to move on she gets up and walks right with them. When they stop she immediatly sits down again. I cannot see anything wrong with her, he knees don't look weird or swollen, nor her feet, she does not appear lethargic. She is just a little smaller than the other 3. Any advice?