My duck hatched 5 eggs sunday morning. One of the ducklings look a little smaller than the others and has trouble walking. Before it could walk about a foot and then would take a break and keep on going but now it can't even walk at all, it can sort of swim though. I checked it out and one of the legs look injured. I'm not sure if it was born with a disability or got injured. The mother sometimes accidentally steps on the ducklings so perhaps it got injured from that? Please help!