Cleaning products......

White distilled vinegar. Kills 82%

3% hydrogen peroxide to water 

1 cup borax with 1 cup water.

Best way to prevent mold, keep bathroom door open after using the tub and shower, open bathroom windows, bathroom fan, and air circulation with ceiling fans or free standing fans.

If there is dis coloring on floors, there may have been a water concern in the past that was corrected with caulking around tub / shower areas and has dried out. A moisture probe can be used to see if moisture exist.

You may have a bathroom without a ceiling exhaust or a window, leave bathroom door open and open another window close by. Ceiling fans and free standing fans really help.