Can a muzzle brake cause crown erosion?

I had a Holland QD brake installed on my Savage 10FP .308 about 300-400 rounds ago. The gunsmith was Mark Pharr. We both looked at the crown before he installed it and agreed it was sharp. It was shooting some tight groups at the beginning. I noticed lately I hadn't be able to pull off those half inch 5 shot groups, so I figured it needed a cleaning. I was looking at the muzzle today and noticed that the bottom half of the crown is not sharp anymore but the top half is. The directions for installing the brake state that the muzzle should be flush with the first port. The Savage barrel has a recessed crown that sits back about a 1/16" and I should note that for whatever reason the muzzle sits back about a 1/16" from the first port. I cleaned with a Dewey bore guide, Tipton carbon fiber rod, brass jag, and Butch's. I have cleaned 3 to 4 times in 475 rounds. Could the brake have caused the crown to lose its sharpness on the bottom, or did I do it somehow by cleaning it? I will try to get pictures tonight if possible. Any opinions would be greatly appreciated.