Sorry for your loss of your flock but I am a bit confused by the link. It refers to teflon on cookware what does it have to do with the bulb you were using? If it were in the bulb how did it get out? Could it been something else like cholera or botulism? Or some type of poison? Weird.
I was confused also. That is why I asked the questions I did. I looked it up. I see that because it is coated that it could produce a gas. Here is what I found and did not seeing any brooder light or heating light.
http://www.covershield.co.uk/
It looks to me that it is industrial and home use. The more I read it is not a coating at all, it is a covering for light bulbs, big difference then it being a bulb. Might be wrong but that is what I found on google.