For those who had been missing them:
Both tractors stalled out when I went in to start uploading the video... iced fuel filters for everyone!
Luckily they both had managed to get a little heat into the blocks by the time the filters iced, and they thawed by themselves with the fuel flow stopped. I put a healthy glug of Diesel 911 into both fuel tanks and they fired up easily again.
I left both running for nearly 1/2 hour before trying to throttle above idle... That gave enough time for the Diesel 911 to work it’s magic, and get some more heat into the fuel too. No further problems after that.