Since u have the fluid out. Raise the caliper remove the pads check and relube. Basic service, then I always try sliding the brake caliper piston back and forth about ten times with air pressure+ Then you can feel for yourself how nicely the piston slides back and forth, telling what condition the caliper is in. I allways do this to any disc caliper. The seal only moves as the pad wears out, the piston does not "slide" thru in heavy use like eveyone thinks. The piston seal flexes and slightly rolls on the piston as the piston makes its 1/8 travel. Because of that the piston and seal bind, corrode/ oil film oxidizes leaving more gunk..... piston starts getting more and more friction till one day you realize your brakes have sucked for 6 months but you didn't really notice.
I need to build up some posts for my noob status sorry i get long winded