We had two of the coldest weeks we've ever had here and I hadn't realized how cold the ambient temps got in the room. It was totally my fault, and I've never had this problem before in the 4 years I've had bps. Now I have a heater in there for the rest of the winter to ensure it doesn't happen again.
I'm sorry for your loss. Very glad to hear the others seem to be recovering.
Thanks for being brave enough to admit your mistake and to share it so that hopefully others can learn and avoid the same problem.