Volume fade

Hi everyone,

I have a tube amp and preamp, a Sophia baby and an audio experiences preamp. Last night as I was listening to music, the volume slowly faded off and bottomed out. Now I must turn the volume over halfway to hear much of anything, and it still sounds distant and compressed.

Does this sound like tube failure? I'm pretty new to this, and am not sure what to expect when a tube wears out.

Any advice is welcome.

Thanks!