Not sure if I’ve ever mentioned this, but one piece of advice we give all of our commercial building mgrs/staff that we clean regularly for is this. Glue a penny to the bottom of your mop buckets. If you can’t see the penny, it’s time to change the mop water. Very common for janitorial staff to use one bucket for all of the tile (it’s clean after you wring it out right?), which is why their tile/grout get dirty so fast. No different than the vacuum with the full bag that never gets emptied but is still expected to do its job.