Tung-Sol kt170 tube started glowing brighter

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

That's what I wanted to be assured of.   Thanks

@kitegod , Yes, you can replace the one bad tube with one with similar numbers on it and then check / reset bias. If your amp isn't rated for the KT170 despite being told it should work it might be safest to revert to the tube types that are specifically compatible with the amp? I guess the other option is get the new KT170, install it, check bias and see what happens- it may have been an isolated incident with the one bad tube. 

@OP The tube is starting to red plate. Don't try to rebias the tube as it will only hasten it's demise.

With only 50 hours on the tubes why not try to get a warranty type replacement from seller?  It sounds like you were sold a bad tube.