id put $20 bux on this
jack up and support
remove the front wheels
using screwdrivers push back each side caliper pistons 1 side at a time i.e. rf inner pistons, (have someone push the brake pedal and watch for sticking pistons), rf outer pistons, (have someone push the brake pedal and watch for sticking pistons), lf inner, lf outer.
i'd bet you have one of the pistons sticking in the caliper and it needs replaced.