Several of my chickens have died from a disease I can't identify. Symptoms include runny nose, loud breathing, blood spots on the rooster's combs, -which, right before they die, turns somewhat blue, gets thin, and droops- extreme thinness, runny droppings, and in one case, a large cyst or something on the rooster's leg which popped and attracted maggots. The leg itself got a lot better with antibiotics, but the rooster died. The hen I'm wondering about now is eight years old, mixed breed (I think) and probably around 4-5 pounds. She has trouble breathing, has dropped to the bottom of the pecking order, (she used to be at the top), seems to be losing her eyesight, and is slowing down from her normal active self sometimes when I carry her or she tires herself, her face turns blue until she catches her breath. I think several chickens have died from the same disease because some of the symptoms are common, but if it is the same one, it takes several months to spread from one bird to another, and over a month to kill one. If this sounds familiar to anyone, help would be very appreciated, as this hen is a longtime pet.