So I love my Ashdown, BUT, I've run into a problem....

I've had it since, I don't know, May, and recently I noticed the speakers sounding a little overdrive/distorted at basically any volume with basically any EQ setting!

Is it because I've been pushing my cab too much? Could it be because the ohmage isn't equal, the head is 4 ohms and my cab is 8 ohms.

This is quite upsetting because the cab is rated up to 450 watts and the head only puts out 300, well 307 to be exact, but who's counting

Thanks in advance guys.
-Fender Deluxe Active P-bass (60th anniversary)
-Peavey T-40 (1982)
-Hartke HA-3500
-Aguilar GS 2x12
-GK Backline 2x10