In my experience, ravello is prone to these kind of black "stains" over time. I had a pair of ravello PTBs and a pair of ravello tassels that ended up looking exactly like this after heavy wear. The shoes seem to darken a bit in the creases. I would just wear them to see if they even out. The staining doesn't look bad to me in the photo you posted (the shoes still look very good IMO).
Thanks For the advice! happens that the liquids really been absorbed by the shell, now some more brushing and they will ne back in my feet 😁