We purchased 14 chicks and all has been going well, all the chickens are 3 weeks old and were active, eating and drinking. No signs of any problems, at 3 weeks the brooder temperature was 85 degrees. Yesterday we went to check on them and all 14 had died. Our brooder is in the house so they are well protected. We have no idea why they died, especially all at the same time.. i.e. within maybe 6 hours. We had changed their food and water in the morning and that afternoon when we went to check on them... they were all gone..... Need help in understanding why this happened.