SICK Rhode Island Red 6 weeks old

[ABCChicks]

I have a 6 week old RIR who appears to be sick. She is feathered out and won't stand up. She has a good appetite and will drink.. Her poop appears to be normal. Where do I begin to research what could be wrong? This is my first time raising chickens, we purchased 5 dibs, the other 4 appear to be normal. I have isolated the RRI from the others so they would not harm or bother her.

 

[Wyandottes7]

She might have a vitamin deficiency. Vitamin deficiencies can cause birds to be unable to walk. I'd get her started on some vitamins. You can get either special poultry vitamins or Poly Vi Sol infant vitamins.