I've lost 3 broiler chicks that are 2.5 weeks old. They were vaccinated for Cocci and Marek's disease and came from MurryMcMurry. All three have been fluffed up, standing still, eyes closed. I've not seen any bloody stool. I've given them appropriate food/water/space/light. They've also had Nurtri-drench. They are part of a 49 bird bird chick flock so I'm a bit freaking out that is going to continue. Ideas on what it could be? The current one has a large crop right now.