Lskellenger,
Thank you for posting about this very important issue. I know it was very painful for you, but you have informed a lot of people and may have saved other flocks. Five very important things came out of this discussion.
1) Whenever a bird dies, their necropsies can sometimes give you answers and aren't that expensive if done through a university vet school or state avian disease lab. Whenever numerous birds die, finding out why is essential.
2) Resist the temptation to blame the obvious. Look at the total picture and you will always find multiple possibilities.
3) Birds rarely need extra heat if they're healthy, but they do need ventilation and enough space.
4) Teflon coating is deadly to birds when heated (via light bulbs or non-stick cookware), and cedar shavings can be as well.
5) And this is new to me -- there's a heat lamp on the market that is Teflon coated! Was this truly a heat lamp, or was it just a light bulb that was used for heat (like the GE rough service 100, etc)? Was it a red heat lamp or a white one? Do you still have the packaging, or can you still read the brand and bulb type on the bulb itself? If not, can you go back to the place where you bought the bulb and get the information and post it for us? (And if you haven't already done so, please ask the manager of the store to post a big sign, and put labels on every box, that these are poisonous to birds -- mammals don't have a problem with this. Also, please contact the manufacturer and ask them to label the bulbs as being deadly to birds -- Sylvania and Phillips already do this, GE has gotten sued many times for this but still refuses to do so -- but another bulb company may not know about the dangers.) I know this may be hard for you to do, after what you've been through, but you could be saving someone else's flock by taking a stand.
I'm so sorry that you had to go through this. I hope your new girls love your rooster.
--April