I'm sorry for coming in this late in the conversation, but was it the teflon coating on the heat lamp that poisoned your hens or not? I tried to skim over this thread, I'm sorry.. just want to know.
If so, how can one be sure the heat lamp they are using to heat their coop doesn't have this coating?
Yes...it was concurrent with teflon toxicity poisoning. You can check the packaging or call the manufacturer to make sure.