It very well may be that the tweeter has started to go out.
I'm going to a local B&W dealer tomorrow to listen to some new speakers (704, 703, CM7, 804S, and centers).
I will bring my CC6S2 with me to we can try it out there next to the other centers.

They have some very high-end Amps and Pros there.
I'm wondering if I replace my 10 year old DM603 mains with higher quality mains, that my 990/7125 could be holding them back.