Baby chick with walking issues

[ChickenLadyCrissy]

we have this sweet little chick that we think was injured somehow. She was 100% walking normal for about 2 weeks and then we noticed she was sitting all the time. She has one keg that is strong and the other is almsot useless. We have been putting her here in this chair with her feet like so to try to help. As soon as we saw the issue we got some stuff to add to the water that has riboflavin in it. She is eating and drinking as normal and in her own box. I am worried about her being alone. She seems to favor and not use her whole right side. Any therapy ideas? Any idea what may have happened?

 

[KingD]

What is the brooder like?
Any pics?

 

[ChickenLadyCrissy]

What is the brooder like?
Any pics?

The brooder box is a large kids swimming pool. We use puppy pads and hay for the bottom. None of the others have had this issue. They are all about 3 weeks.