The heavy-duty cleaner I use in the video is made by “Miracle”. It’s called a Heavy-duty ACIDIC cleaner. It’s a professional-grade cleaner for grout, tile, and non-polished marble, granite, and other Natural Stone. Being that it is an acidic cleaner, I would recommend wearing latex gloves, eye protection, and mopping your floor with water once done cleaning your grout.
Really it's just the matter of using a good grout cleaner just like I did in the video. If it was white before it should come back..
What if I have white grout in my bathroom, how do I get it back white instead of gray?