I currently have 5, 4 day old Silver appleyards. I got them from a local farm and feed store who ordered them in for me. They are all doing good except 1. He/she seems to have part of the yolk not fully absorbed. (Its not the vent). Its black and seems to not be going down in size. Ive been watching it closly, the duck seemed to not be effected by it until yesterday. Its slower than the rest, slightly smaller and not as active now. I cleaned it up today as it was looking wet and had a small odor. I am considering separating it from the rest and giving it some electrolytes. They are getting non medicated chick starter that is 20% protien. I will attach pictures of it. My gut says leave it be, but it seems to be effecting it now and i dont want to loose this duckling. Should I add niacin and Vitamins? Brewers yeast? Is this something I can remove? Should i seperate it? If i separate it, should i include another with it to keep it company? Or close off a corner of the brooder so it can hear the rest? Supplement it? Any advice would be appreciated. As a side note, I had a injured duck last year that was attacked by a racoon and i was able to jurse it back to health. So i have a little experience, but I've never seen this.