I have a 4 week old Peking duckling that is not acting like the others. I noticed he had very turned in legs about a week ago and read to supplement niacin and brewers yeast. I have been and have not noticed any improvements yet. He also does not seem to be growing as much as the other Peking duck and just doesn't seem to be as active as the other. Now he is showing some new symptoms. Yesterday I noticed that he has a reddish orange spot growing on his bill. Also, he has a dark colored diarrhea. Please help!