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.


@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.

I'm pretty sure you are seeing an event called "Red Plating" which is the tube overheating. There are a few causes- and finding them can be a mystery. 

The tube could be shorting (doubtful given what you've described)

The bias is certainly off. How could I know that? All biases are off at least a little. Add time, other component deterioration, and mismatched components and it's a boas nightmare. 

I had a mystery red plating problem and it turned out to be a bad 12BH7 high current driver - which caused me to have to replace 2 6550s. OUCH!