Black spores on York stone flags

[On one]

I went to do an initial clean on a newly laid York stone floor today(not laid by me)
As the floor was covered by protective sheeting and dust etc etc I couldn't see much of the stone floor..........any way it hasn't come up clean using Lithofin Power Clean, a rotary scouring machine and then the waste water vacuumed up.
The black spores have obviously been a feature for some time before being salvaged and stored. They will come off with some intensive wire brushing but this isnt going to be possible for the 30m2 that remains unclean.
So what (Lithofin) chemical will remove the spores, if any?
One for @Lithofin BOB me thinks

 

[Old Mod]

If you don't tag uncle Bob, he won't know you need him. 🙂

 

[On one]

If you don't tag uncle Bob, he won't know you need him. 🙂

Just for us computer dimwits, please tell me how I do that again(for umpteenth time)

 

[WetSaw]

Just do the @ symbol and start typing their username and a pop up will pop up with names and you click on the one you want @wrighty

 

[On one]

@pdc

 

[On one]

Yay!

 

[Lithofin BOB]

I would test , lithofin outdoor cleaner if the whole floor , or mildew away if on just a couple of stones.