I am looking for a cleaning solution for cemetary markers?

https://www.iscga.org/how-to-clean-a-gravestone.html

Have you tried using a power washer and bleach?

Marble, granite, and stone do NOT like having acidic (ie: citrus-based) cleaners used on them. Citrus or vinegar will actually cause “etching” on granite/marble. Not a good thing. Granite/marble also don’t like it when you use something like Windex on them because it strips the “seal” off of the stone.

Any acidic cleaners will etch, dull and stain the surface, including vinegar, citrus cleaners, and lime/calcium cleaners.

Homemade Granite/Marble Cleaner, 1/4 cup of rubbing alcohol (or cheap vodka), 3 drops of Dawn or other dish soap (Castile soap would also be a good alternative if you prefer), Water, 5-10 drops essential oil (optional – to help mask the alcohol smell).

Put the rubbing alcohol or vodka into a 16 oz spray bottle. Add the dish soap, essential oil and fill up the rest of the bottle with water.

If the stain is persistent and is still there you can try removing it with ammonia solution. Make the area of the stain damp with 10% ammonia, diluted in water. Ammonia is knows as a base solution, so it is suitable for removing stains from granite/marble.

The final stage of the stain removal us rinsing. Rinse the solution from your marble well to eliminate any residue, left from the cleaning ingredients on it.

Get a stone cleaner. Wal-Mart sells different brands for stone, marble or granite. Also a product called "wet and forget". Look on the internet on where to purchase.

30 second cleaner you should be able to get it at Home Depot or Lowes

https://www.goodhousekeeping.com/home/cleaning/tips/a2456/headstone-caring-oct01/

Thank you everyone