I have a chicken that is weak and wont stand. It is laying with both feet on the same side. Most of my chickens (40) have come down with the avian pox. I lost a couple already that were young. This rooster has has a resp. issue for over a month. He wheezes and coughs. I assume it is the avian pox. But just to rule out mareks, I looked up some symptoms and the eye discoloration was listed. My roosters eyes still look 100% healthy. Could it still be Mareks?