This morning I found one of my 2.5 week old ducklings on its side, and it couldn't get up. She had dug a trench around herself (It looked like a dust bathing hole.) so I think she had been there awhile. When I lifted her up, she couldn't stand by herself, leaning heavily on my hand. (Even though she is terrified of people.) Her wing looks like it doesn't have anymore feathers/fluff on it. Whereas also very dirty. I gave her a bath (which she drank half of.) And gave her food and water. She is currently wrapped up in a towel under a heat lamp. She can wobbly stand on her leg, but when I tried to put her with the rest she got trampled and fell down. She is the runt, just half the size of the others. I don't think she can survive with everybody else, but she misses her friends. What should I do? I've been giving them niacin, so I don't think it is leg troubles. Then others are fine.