My G&WT2.6f hybrid amp keeps burning the right channel tube ... any ideas?

Hello everyone, This will be my first post in a long while...perhaps some of you have a clue as to what's going on...my trusty old backup rig which i use intermittently first gave me problems last holidays when a tube blew on the right channel ... i assumed it was a bad tube - the flashing on the inside top of the tube was gone and the tube was clear with a slightly white tinge to the innards; the base was fragile and cracked upon removal ... so i put the amp away for the winter, and just returned to my summer location and set up the rig last week ... i replaced both e88cc's with nos mullards and had a great night of listening with my bada tube cd player and sony sa5000's ... after listening i powered it down, pulled out the power plugs, and covered it up ... tonight i was going to listen again and lo and behold the right channel tube has its top inside flashing gone, white tinge, and fragile base which also broke when i removed it ... i'm pretty sure its the amp (unless both tubes happened to exhibit the same failure) but i never had tubes go as described ... as i only paid a couple hundred for the amp 4 years ago its no big loss and not worth fixing even though the sound is really good ... can anyone confirm this type of tube failure or condition in this amp in particular or hybrids in general ... thanks a bunch

if it was one tube i would agree with you, but two tubes from the same socket indicates an underlying problem ... i am also quite anal about tube handling and insertion (Michael Scott: "that's what she said") ... anyone else care to spitball? a buddy of mine is of the opinion, and I agree with him, that something in the ss section plotzed, caused the tube to excessively heat leading to catastrophic tube failure