We purchased two dozen chicks from Meyer, and they will be 13 weeks old tomorrow. Starting around week 7-8, these chicks started dieing from an unknown cause. The chicks that passed were large, appeared healthy, active, etc. We lost our 5th chicken today. This morning, all chickens were fine. I went out to check on the chicks this afternoon, and found her laying within the coop. She was lethargic, eyes half closed, curled up, etc. I brought her in and tried to doctor her up, but she died within the hour. She was acting just like the first dying chick that I found around week 7-8. The chicks were all vaccinated for Mereks at the hatchery. They have been on medicated chick feed. They have received some layer feed when we ran out of chick feed, but it hasn't been much. We have a separate coop full of laying hens, and they've all been doing well. As far as we could tell, their poop has been fine. They're not wheezing, making weird noises, or acting weird. They'll just be fine one day, and dead by evening or by the next morning. Any ideas what we can do?