I started my flock about five years ago from birds I bought at a flea market. Two years later I added to my flock by raising some RIRs chicks I bought at a local feed store. My flock has been really healthy up until I added some new birds this year I got from a friend and a couple I bought from a breeder. At first, one of the rooster I bought from the breeder got into another pen and fought with one of my other roosters. He was beat up pretty badly and I tried to nurse him back to health. He healed from his wounds, but he started sneezing and then later he developed breathing problems (sounded like trying to breath through a runny nose). He walked around like whipped pup and would barley eat, never crowed and would not even try to flirt with hens. I separated him from the flock and treated him Durvet Duramycin 10 that I got from tractor supply. It did almost nothing for him. As long as I treated him continually, he would seem a little better, but as soon as I stopped treating him, he would go right back down again. Later I treated him with Sulmet, and it did help him, but he would get sick again after a week or so. After three months, I finally put him down to end his suffering. I thought I was done with the problem but then I started noticing that some of the pullets I had hatched out this year were sneezing. Not a lot, one here and there. I never separated them from the rest of the birds and and it does not seem that any of the other birds ever got sick although some of them continue to sneeze even now. They seem healthy otherwise. But then some of my older hens started to to sneeze and develop the same breathing problems that the rooster had, and all of them eventually died. What is confusing me is this. I have a large free range flock of over 75 birds. Not all of them have this sickness, even though they roost right in the same coop as the few that do. What ever this sickness is, it seem to only effect certain birds. Some it kills, others live fine with it, and other have completely recovered on their own from it. I have not had a vet officially diagnose the disease yet, but let's just assume it might be MG for now and go through my choices of action. I assume the disease is contagious and if it is, then my whole flock is infected. If it is MG, then they are carriers of it, even if they are not sick. I have invested countless amounts of money, time and energy into this flock. I just don't know what to do. I know the best solution if it is MG, is to get rid of my flock and start over, but good grief! This cannot be the only way to handle this, can it?