Our hen isn't behaving normally. Plymouth Rock, about 1 1/2 years old. She has her feathers ruffled out, some seem "out of sorts", her comb is not the normal bright red, but dull and mottled in appearance. We have separated her from the flock and offering her food and water. She will sip water if offered by hand. We have not noticed her eating since yesterday. We have apple cider vinegar added to the water. Offering mealy worms, along with her regular feed. Any guidance would be appreciated. We are new at this and have not encountered this before. She is inside. Thank you!!!