I am not sure that is marble. @DeGiCo Media - please say what material the tile is.

There are companies that can buff the tile and use a special commercial cleaner along with their buffing machines to get the grout cleaned. But you need to know what is the material of your tile.

@M Miller How does one go about determining what the material is exactly? Sorry. I know it's not vinyl that's for sure. How to tell if it's marble or ceramic or something else?

I would get a professional grout cleaning and then use a grout renew product to paint and seal the grout to even the color

Hire a professional to restore the tile and the grout. I live in cindo and the buildijg periodically restires the limestone tile and grout and it looks like new

@millworkman We have steam mop. It doesn't work well. We go through three mop heads every time we attempt to clean it and it still looks filthy.

We rented a house while building that had light beige ceramic tile and grout. We have 3 dogs so things got dirty, even with regular cleaning. When we moved out I hired Stanley Steamer and they did an amazing job getting the tile and grout to look brand new. It was cleaner than when we moved in!

I am going to suggest krud cutter a stiff nylon brush and a rinse bucket. A lot of elbow grease, but mopping is not going to do it. This is a hands and knees job. Once the tiles are clean you can use grout renew for the grout.

I had a Shark steam mop too, but the professional steam cleaners are much better. I was skeptical, but they did an amazing job on my tile floor.

https://www.youtube.com/watch?v=D7sTymORypQ Andrea Jean Cleaning has great videos on how to clean grout! You should try this one!

SO MUCH BAD ADVICE! I'm a wood floor person and even I know that you're not supposed to use harsh chemical, basic or acidic cleaners on stone.

I initially wondered it this was real stone or a glazed marble-look tile. The bigger picture shows a random patterning with no repeats so I'm pretty sure it's real stone. Real stone floors require a neutral pH cleaner. In addition to not cleaning your floors properly, the products you have used are probably making the problem worse. The floor needs to be resealed after a thorough cleaning.

I suggest you engage a professional to use the proper cleaner and a floor scrubber to remove all the grime from your floor, then apply a proper sealer. This will make your floor look nearly new and be much easier to clean with the correct neutral pH cleaner.

If you're hardcore DIY, you can likely find the correct cleaner and polish, and rent a scrubbing machine, which I think will be necessary to do the job right.

Just came across this product re our brand new but very smudge-prone LVP. Apparently it removes assorted gunk and might be worth checking out. https://www.amazon.ca/gp/product/B00GTXVWDQ

I use a good cleaner, whatever is recommended for your tile and an old electric tooth brush after a bit of soaking it comes out great, then seal.

Are you talking about the grout or flooring? I just found this video and gave one dirty line of grout a try, and it worked! Our grout line is wider and I used a stiff grout brush.