I will use the suggested guidelines to ensure thoroughness:
1) What type of bird , age and weight (does the chicken seem or feel lighter or thinner than the others.) Barred Rock hen, 7 years old, seems underweight compared to the others in the flock.
2) What is the behavior, exactly. Walks...
More information : my other 3 chickens are just fine. My father put some diatomaceous earth on them just in case it was mites. The two chickens drank a bit and ate the cheese I tried to give them (the blue one wouldn't take her food) The red one seems in a better shape, she walked a bit and ate...