I have lost two birds to this a few months ago and now all the sudden I have two more with the same symptomes. They start to loose the strenght in their legs and it just gets worse and worse until they tip over. The first time around I treated with vit b drops and antibiotic. Didn't help. This time I have started vit drops and put nutritional yeast in food to help with vit b if that is the issue but I don't know what really is causing this or what to do. My ducklings started doing this when a few weeks old and I was told to increase vit b and that the food they were on had too much protein. I was hoping that the chicken problem was similar but they are still on chick grower and about 4 months old. Please, if you have any ideas please let me know before they get worse.