What could have gone wrong?

I have enjoyed my analog system until today while playing and in the middle of music all of a sudden it has lost its wide soundstage and imagery, the stereo spectrum became so narrowed and lost its sense of musicality .
And sounded they are coming from the center and afar..
All my system are tubed preamp, amp .
Any piece of audio wisdom of where to start to trouble shoot?
Stylus / Cartridge

Best of Luck

If you have any other source; cd player, music streamer, even a cassette deck or tuner would help you determine if the source is the problem or if it's the amp or preamp.

It sounds like you might have a tube(s) that went down.
Check your preamp esp. the tubes. The first thing I thought of was a tube/s starting to fail, as I often credit them for throwing the 3D stage that much tube gear tends to exhibit. The preamp is central to everything so...