I have read that with my Cornish X I could lose up to 15%. They have been here ~84 hours and I have lost two (out of 26). One on day 2 and one on day 3. They just died in the brooder. Vents were clean. Any ideas? Is this normal loss? I thought they would die later on, I'm just surprised I've lost two in 3 days. I worry its too hot. I have 2 heat lamps but when I turn one off the huddle under the the other light. Could too much heat kill them? Thanks.