[Amps] still stumped

[Carey Lockhart, KC5GTT]

hello all,

developed a problem with my amp. with a dead key no signal in the tube starts to get VERY hot. nothing has changed in the amp. i have tried 3 tubes and they all seem to do the same. they also do not tune up past 1200w with 100w +/- drive. the idle current also is high on the meter for amount of bias i have. it takes 56v to get it down to 100mils. had been working great for the past year or more.

2m gs-35b yu1aw lazy builder
4100v plate
29.8v bias = 250mils 

Carey