Just a theory, but maybe there's something in the powder that you put in the water? You could check the ingredients and see if anything could harm her. I'm not very experienced, but it would be good to check. >^< Best of luck! I hope she'll be okay!
This morning, my younger sister brought one of our 12 silkie chicks. It was one of our biggest ones, I don't know how old they are, since the person who sold them to us wasn't counting the weeks. I've seen a few threads about hens and roosters with similar problems, but never on a chick. A few...