Make sure it isnt intestinal lining that was shed, which is normal. Here's the poop chart:
If it's not intestinal lining, purchase corid 9.6% liquid solution at your feed store, it'll be in the cattle section. Dosage is 9.5cc per gallon of water for 5 days. You'll want to treat all your chicks with it.
Cocci can be spread, so yes, if there is any other's in there with her than they will catch it too.
This video will explain what cocci is and how it affects your chicken; enlightening, IMO. Beware, it's a little graphic.
See post #2 on what to do. Cocci can kill your chicks, timeliness is of the utmost importance in treating it. If the feed stores are closed, you can temporarily delay (hopefully) the effects by sprinkling powdered milk directly onto their feed to eat. Get the corid asap.