indian stone slabs - muddy footprints wont come off

[joeshore97]

Hello ive been struggling for days with what might seem easy and minor but its turned into a huger head ache, costing lots trying to fix this

ive got riven - kandla grey indian stone slabs. theyve been laid in the last few months so i heard i shouldnt seal them just yet, so i didnt.

i put a topsoil/sand mix down on my garden to even out some spots, i was mixing it on the patio because ive just put new grass seed down and didn't want to kill it, ofcourse it went everywhere and i must have stood on a few bits. i rinsed it away with the hose pipe and thought nothing else of it. a few days later i went out to water the grass and noticed more than a few footprints on the stone. i then thought ah ill get the pressure washer out, it didnt touch it. so what ive tried in total is;

pressure washer, washing up liquid and a stiff brush, sodium hypochlorite and stiff brush, ive tried hot water and a drill brush,
ive tried steaming it out, ive used normal househould bleach after i thought the sodium hypochlorite may have been left out in the sun too long and died or whatever, ive used lithofin MN power clean with a drill brush and scrubber pads to try and get it off.

NOTHING has worked at all and there still there, im just trying to remove these before i do seal it and have to look at them forever lol..


has anyone got anything that can deal with this im at my wits end lol ?