Another update on my situation: Alkalinty is now at 50 ppm and pH has gone from 7.3 to 7.4 over the last 4 days without adding any muriatic acid; a vast improvement. We'll see how it goes from here but I'm very hopeful that my acid comsumption is going to go way down.

As to my original theory, from all the stories I've read here and elsewhere, I'm becoming covinced that it's at least somewhat valid; SWGs themselves are not the underlying cause of rising pH.