sorry typing and not contrasting, glad to raise a smile(must learn to read before I post, never do,sorry)
Marble is very sensitive to some chemicals, even shampoos and products can ruin it, it might be hard to prove.
When we have cleaners in to some of high end properties(construction and property management), we are very careful to go through what can be used where (product and tool), as some finishes are very sensitive , as are septic tanks and klargester.
It can be fixed.
we label what product can be used where, and make sure that anyone on the property is aware of why, I try not to have damaging products in the properties, because there is always someone who thinks, flash, fairy or bleach is a good idea,
In future stick to ecover products when you have untrained people in the house.
It's very easy for someone who is use to using the harsher products to automatically use them, or use contaminated cloths/sponges.
I switched to a policy of not having harsh products in all the properties twelve years ago,and we haven't had any surfaces damaged since.