My RIR hen "Rita" is 4 or 5 years old. I almost lost her about 2 years ago to an unknown sickness. She went from about 5 lbs to less than 2 lbs. I was able to nurse her back to health and now she is one of the heaviest hens I have. Her molt at the end of 2015 went perfectly and she has nice shiny feathers, healthy looking bright red comb, and lively eyes. Rita is very active, she can and will run, she bosses most of the other hens around, and she eats well. I've noticed for a few weeks now she is breathing loudly/heavily compared with the other hens. I have a feeling it could be age related. She stopped laying about 8 months to a year ago, and some of the hens that she came with as a chick have already passed away from natural causes. I clean the coop every 1.5 to 2 weeks with a full change out of nest hay and shavings for bedding. None of the other hens show any signs of illness (there are 7 total). Anyone have any thoughts of what Rita might be suffering from?