My week old icelandics are doing great, except for one tiny chick that is half the size of the rest. I noticed after getting her that she had pretty bad pasty butt. I was able to clear it up, but now she has a very large crop and isn't eating well. We started giving her infant oatmeal with probiotics and water with acv. She is weak and unsteady, but is chirpy and seems like a fighter. She is in her own brooding box to help keep her from getting stressed. The threads I have read about slow/sour crop seem to only pertain to older birds. Any advice/suggestions for my little one?