Hi,
Would appreciate advice,
These patio slabs were laid recently and have these stains as per picture. I read online that these fade after a few months but am wondering if there is any way to remove them. I've tried scratching a small area of the very dark marks and that scratches off but still leaves a grey outline underneath. My power washer with the patio attachment doesn't seem to shift the marks. Would be grateful for any ideas. Thanks in advance.