i have almost 4 wk old ducklings two are peking ducks .... and i noticed a few days ago that the one had bowed out legs and and it seems the heavy that she/he gets the less they can use the leg and get around!!! today is the first day they havent been outside all day as i still keep them in the brooder in my house at night but a cold front came in and they have been inside i noticed a little while ago its seems that he/she can no longer hold weight on this leg. they are eating fine and drinking and swim okay but they others are much stronger and i am at a loss on what to do with the leg someone please help me if they can and advise me what to do ? im afraid i may have to put it down but i wanna know if there is anything else i can do ? is this niacin deficiency ? i have been feeding them all the same thing the chick starter food and adding in some yeast every other day this duckling seemed to have this problem from the very beginning ? is there anything else i can do i dont wanna separate cause they dont like being alone i didnt know if i upped the dose of niacin if they would be okay ?