Clean floor, dirty grout

My robot does a fantastic job cleaning my tile floors, however, the mops seemingly aren’t able to reach the grout. I vacuum before running the robot, I always use the “deep cleaning” mode, and I run the robot multiple times, and I still have dirty grout. Does anyone have a solution for this?

I had all white tile and grout before, the only thing that would get it super clean was making an oxiclean paste to scrub the grout with. Scrub and leave in place for a bit, then mop it up.