I am going to replace the pads and inspect the calipers. Since these are GM single piston floating calipers, the problem may be the caliper is hanging up. The piston is pushing the inboard pad into the rotor but the caliper is not pulling the outboard pad into the rotor with equal force.
I may replace the pads, calipers and rotors. I replace the flexible brake lines two years ago and they seem to be in good shape with no kinks.