All my hatchery chicks are sick or dying. They're 10 weeks old now. I've lost a bunch of them and of the ones that are alive, half are sick. They have crusty eyes to the point of them sealing shut. They have a little bit of a runny nose too, but not overly runny. Some are gasping for breath before dying, others are just dropping dead. No real sneezing, no coughing. We did a necropsy and there's no blood or mucous in the trachea. We've also lost one older silkie that was in with them. She was about 6 months old. Another silkie with them was sick, but seems to be recovering. No other birds have been affected. I have a main flock with 50 or so birds, both purebred and mutts. Ages range from 7 months to 3 years. No troubles at all. A mama hen and her babies that hatched 4 days ago, no trouble either. 2 week old meat birds, same thing. No one else has any eye trouble, no runny nose, no sneezing and no death. My marans in the pen beside the sick ones are fine too. What's going on? Any ideas?