The last few days of playing, after about 10-15 minutes of playing, the volume on my MESA Express 5:25 cuts down to practically nothing. It won't go back to normal until I leave it off for a few hours, but then it will do the exact same thing after 10-15 minutes of playing. Is this a sign that it's in need of new tubes? If so, can I get a recommendation for some new tubes? It has 2 EL-84's for power tubes, and 5 12AX7's for pre-amp.
PRS SE Custom 24
Jackson DKA7
Gibson Explorer
MESA/Boogie Express 5:25

Dunlop Cry Baby Classic
VOX Joe Satriani Ice 9 OD Pedal
VOX Joe Satriani Time Machine Delay Pedal
Ernie Ball Strings
V Picks
That's the first, simplest place I'd try correcting the problem. PM me. I have a few sets of EL-84s from my old 5:25 that I have no foreseeable use for. I'll send them to you for nothing.
Parker Fly Deluxe
Various Strats
Koch Studiotone XL
Koch Startrooper
Quilter OD200, 101 Reverb
1958 National lap steel
Eastman El Rey 1