1 of your chickens has mucus coming out of its nose its also off its food can you tell me whats wrong?

The mucus build up is common and can be treated with Apple cider vinegar. Add two tablespoons of Apple cider vinegar to each gallon of fresh water for 3 days and allow no other source of water to the flock. This will treat both the healthy hens as a preventative and those hens already suffering. Keep in mind not to do this more than the three days as it becomes less effective the longer you use it. Cider vinegar cuts through the mucus and helps the hens clear it out. Your hen is not eating because it cannot breathe well. You can also source a tonic from your local feed and grain outlet. Polytonin A or a water soluble tetracycline will help clear up respiratory problems.