Buzz in my Martin Logan Sequel II's

I've developed a sharp buzz that sounds like it comes from the top part of the electrostatic panel of the left speaker, but only at high volumes with certain CD's. It's never happened with LP's, and otherwise at lower volumes the speakers sound fine. I'm the second owner, speakers dated 1986. I've had them for 14 years. Is this the dreaded "time for new panels" or can something be fixed keeping the current ones? Is there anything else it could be? I'm assuming amp clipping would be heard in both speakers, right?

Thorens 166 II, MC Gold, NAD 3130(phono), Moon Equinox SE, Sonic Frontiers SFL-1, Classe 70, Martin Logan Sequel II