I am really confused. Our chicks have been doing great, they have been out in the coop for almost 4 weeks and were still doing great, Saturday I went out and 9 were dead, today is Tuesday and when I went out this morning I found 5 more dead. The only thing different for them is about a week and a half ago I bought a different kind of food still it is a starter/grower just different brand. They get fresh water daily. They have a light in the coop for heat, the coop has ventilation, they have a large run. I am just really confused. I have had all of these chicks since they were a day old. Please any ideas?