Not sure offhand what kind of bedding it is, I'd have to look at the package. None of the birds have done badly with it before, though, so I suspect it was being cold when the electricians were here leaving the door open or the night the heat lamp blew out in the middle of the Brrrrrr... cold night.
Sandra, I'm sorry for your loss. I'm like you, I think it's more likely the heat situation than the shavings. Best of luck with the rest of them.
ETA: Mine started out on pine shavings, still use it to this day. I made the newbie mistake of forgetting to put down paper towels over the bedding for the first few days. Didn't matter, they still did fine.
Very young babies should probably have the shavings covered until they figure out where the food is. They will try to eat it, and can't handle it yet. So cover with newspapers or papertowels for the first few days until they know the difference between food and bedding. I try to keep my chicks on the rubber shelf liner in smaller brooders for the first week until they stabilize.