Baby Chick Problems
Can you post pictures?
Sounds like possible pasty butt. Gently wash her bum in warm water to remove the dried poo. Make sure to dry her good. You can apply some Vetericyn ointment or plain neosporin to the raw area. If it is bright red and noticeable you may need to dab on a little bluekote to cover the redness so she doesn't get picked on by the others.