Don't reuse the tube that glowed red (not worth the risk).
Pretty certain the P2 has individual bias adjustment for each power tube and if this is the case pick up a new replacement and bias it per SF's instructions.
DeKay
Tung-Sol kt170 tube started glowing brighter
I installed 8 Tong-Sol kt170 tubes in my Sonic Frontier Power 2 amp. One tube started glowing a bright orange, yellow at the lower portion. I hear no sound interference. Should I replace it? If so, replace paired, right channel quad or all eight for matching purposes? I did swap the tube into different socket and it is the tube.