Natural Tile and Grout Cleaner
Mix three cups baking soda with 1 cup warm water to form a paste, scrub on well and rinse. Use an old high powered toothbrush to get into the small spaces.
Also try using Hydrogen Peroxide with water in a spray bottle – use half a cup of peroxide with one cup of water. Spray on and leave. What I love about this mixture is it is not toxic like bleach and its easy to spray on. Use daily to prohibit the growth of mold