Confused and need help

What leads you to believe that the Maggies are "going faulty"?  Is it just because they've lost some sparkle?  If so, I'm with @mijostyn.  When was the last time you replaced the tubes in the LS17?  Good NOS tubes in a preamp can definitely bring back that sparkle.  Sometimes it happens so gradually you don't even realize it was gone until you replace the tubes.

2x parasound A21

I presume this means that you have used the two A21s in bridged mode. The manual for the A21 states as follows:

You should not connect a speaker with an impedance of less than 8 Ω to the A 21 when it is configured for bridged mono operation....

... We strongly recommend against using speakers rated at less than 8 Ω when bridging.

The Maggie 1.7 has a nominal impedance of 4 ohms. The Harbeth 30.2 has a nominal impedance of 6 ohms. Both speakers are therefore not good matches for bridged A21s.

Also, given that a single A21 operating in stereo mode is quite powerful (spec’d at 250 watts into 8 ohms and 400 watts into 4 ohms), and given that both speakers have sensitivities in the vicinity of 86 db or so, I would think it likely that a single A21 operated in stereo mode would provide enough power anyway.

And, finally, I see that the Harbeth has a "power handling" spec of 150 watts "programme," which is to say that a single A21 operating in stereo mode can most likely supply more than twice as much power into its 6 ohm impedance than the speaker can safely handle.

Regards,
-- Al

I would go with what rcimci and david_ten mentioned.

It may be you. It may not be your equipment. Or, as they used to say, varietas delectat.

Whatever the reason, if you can, try it at home.