My ducks are about 2 1/2 months old and a couple of weeks ago I noticed one of my ducks had a very noticeable lip. She has a very hard time walking so she prefers to lay down, and is unable to get into the pool herself so I have to get her in and also take her out. I have checked both feet and nothing is wrong. There are no injuries and it seems as if she feels no pain. I have 6 other ducks and 3 days ago another duck started with the same problem just less severe as she can still walk and get in and out of the pool. What could be wrong with my duck? I am worried about her.