I have 4 ducklings, all 4 weeks old and all doing very well with the exception of one Welsh. She is significantly smaller than the other 3, sits often, and it seems very difficult for her to walk. She is a little pigeon toed and still can walk, but after a minute you can see her starting to get shaky. They all eat the same food and live together in the same pen indoors until we can start getting them acclimated for the winter weather. We have been giving her niacin drops directly in her mouth every day for about a week now and have seen no improvement as of yet. We just switched their food from a chick/duck starter to Purina Duck Grower to see if that will help. No injuries, lumps, or deformities are noticeable. Any ideas what we can do to help our little runt get up and running? Thanks!