4 week old Silkie sick

[balbrt1]

I noticed on Sunday evening that one of my black silkies was standing up sleeping . I pulled her out of the cage and bundled her up and held her. She would just sleep as I rocked her. She is eating and drinking. The five I have has noted been in any coop. Just outside last week to soak up some sun. They are not fully feathered out and still so small I will not put them out yet. They will have a coop and run to themselves. Any way she does not have loose stool, no visiable signs of injury and no pastie butt. I have acv in water. I do not know what to do for her. I do have her by herself and she is awake but lying down resting. What can I do?