Hi. I have 5 Khaki Campbell ducklings. They are around 6 weeks old. I have been having a problem with a couple of them not being able to stand for long periods of time. I gave them niacin in their water around 4 weeks, when I noticed the issue. After about a week I didn't feel like it was working. So now I have been giving them nutritional yeast in their food. About a tablespoon for every cup. They all seem to be doing better, except for one. She is always sitting by herself and cant stand for long periods of time. When she does stand for too long her legs start to shake until they just can't hold her up any longer. I don't know what else to do. She doesn't seem to be in pain, she just can't stand up for very long. I don't know if she isn't eating enough food. I also feed them treats ever night (usually peas) and take them swimming in the tub. I am very worried about her and would appreciate any advice. Thanks.