my chicken died without warning

[chicken vs duck]

So this is the story. I put all my chicks back into there coop and the next morning its head is twisted and its laying down dead with pale combs. But my other chicken has exteme lack of energy and I'm afriad that she going to die too. What do I do

 

[Eggcessive]

How old are they? Is there any puffing up (hunching over) or diarrhea? Wry or twisted neck can be a symptom of many diseases, vitamin deficiency, or injury, since it is caused by inflammation of the brain or low blood oxygen. I have witnessed wry neck as a chicken died in my arms from a gizzard obstruction.

 

[chicken vs duck]

They have diarrhea

 

[chicken vs duck]

They are about three months old

 

[Eggcessive]

Diarrhea, puffing up or hunching, poor appetite, and ruffled feathers can be symptoms of coccidiosis. Here is a link about coccidiosis in case you think that could be the problem: http://www.the-chicken-chick.com/2012/12/coccidiosis-what-backyard-chicken.html