Another data point, I'm having the same issues. The anodizing is failing, the calipers are showing chalk like streaks and stains. I've used the same detailer for years, they don't use anything other than auto specific soap and nothing on wheels. The bolts are showing rust, anodizing on the hats are very faded.
The Brembo GT kit I had on another car had none of these issues. Even the anodized OEM calipers on my Spec Boxster didn't look this bad this quickly.
Stoptech said it had to be a harsh chemical my detailer was using. After taking it up with him I'm convinced it's a manufacturing issue, the finishes just aren't up to task.
F80 M3 / Mineral Grey-Silverstone / CCB