Midrange Increasingly Harsh

Lately I've noticed some harshness in the mid-range, especially with violins, clarinets and female voice.  I recently bought a CD of female plainchant, and she hits the un-sweet spot so frequently I can't listen to it.  I don't listen at high volumes, rarely over nine o'clock on the volume knob.  The sound is not anything unnatural, just a less musical presentation and an unpleasant harshness.

I have twenty year old Forest Totems with their original cones, a Prima Luna Dialogue One amp which got new tubes about five years ago and an Arcam CD-73 which got a factory rebuild about three years ago.  I have neither the money nor inclination to just start arbitrarily replacing parts, but would appreciate some insight and guidance on likely culprits. 

Thanks,

John Cotner

New Ulm, MN