with 12,000 miles... and BOTH sides doing it, Its hard to imagine rocks got stuck on both.
Id take it in. No way pads should need replacing at 12K.
On our 2003 Trailblazer, I did once cross a small stream- and afterwards had a grinding sound-
Yeah, there was a rock between the caliper and rotor. Removed it- and all was well.
150,000 on my Traverse and im still on the factory rear pads.
85,000 on the Equinox and still on the factory rear pads.
2013 Equinox LT1 3.6L V6 FWD 88,000
2010 Traverse LT1 3.6L V6 FWD 153,000
2003 Trailblazer LS 4.2L I6 RWD 181,000