If she is also not really eating or drinking, sounds like coccidiosis. You may or may not see bloody poo and diarrhea with it.
When I find a chicken that is 8 weeks or under acting like that I give Corid 9.6% liquid, 9.5 ml per gallon of water for 5 days, mixing new solution daily, as the sole drinking water source. I treat all the chickens exposed to the poo of the sick one. It is a thiamine blocker, so avoid giving vitamins at the same time from what I have read.
Improvement should be seen within 24 hours. It can be fatal within 24 hours...they are feeling gut pain and it can affect their future productivity as well. There are other diseases where they can be not feeling well, too. It is just that I have seen coccidiosis over and over again...I am very quick to treat the young ones for it if they sit like that:
Signs of coccidiosis:
sits in corner by himself
feathers fluffed up as if cold
won't eat or drink
may or may not have bloody poo
may or may not have diarrhea
may or may not have been exposed to the ground (humans can bring cocci into the brooder)
usually 8 weeks of age or under but older hens can get it if immunocompromised or exposed to different soil with a different strain of cocci on that soil
http://www.clemson.edu/public/lph/ahp/disease_links/images/coccidia.pdf
Sulmet treats fewer strains of it. I have only used Corid- in the cattle section of the feed store.
This is just what has worked for me and there are many threads on coccidiosis you can peruse if interested, too!
It is considered an emergency.
Some vets will do a fecal test for cocci for a small fee if you need to have a definite diagnosis.
