I was hoping someone might be able to help me out. I had a 42″ x 90″ x 3/4″ Carrera marble slab fabricated as decking for an undermount tub. The fabricator embedded metal rods (steel I believe) in channels carved 1/4″ deep into the underside of the marble to strengthen the slab. For some reason, the topside of the marble where the rods are lying has become much lighter than the rest of the slab. It looks pretty ugly. The fabricator is at a loss to explain why and says he always uses these rods in marble and has never seen this as an issue. Can anyone explain what went wrong.