Agreed!! Visit one of the illness sites. I would treat the whole flock with tetracycline. My flock had coughing and sneezing last year. Isolated the first one sick, but soon everyone was coughing and sneezing. When you research chicken sickness, it is a little depressing. Everything is bad and causes them to be carriers, etc, etc. Took one chicken to the vet, who told me my whole flock would probably die, but I should try tetracycline. Went to my local, small hatchery. Told them what was wrong and that I needed to pick up antibiotic. Their response was, relax. Chickens will get sick but not every sneeze or cough is a big bad disease. They gave me what I needed, I treated everyone followed by some yougurt and everyone got better, no one died and I have added new chicks a couple of times and they haven't gotten sick either. So, just be proactive. Try to isolate. But, I would treat everyone.