This sounds more like a chemical reaction between an acid—the vinegar—and your marble, which is a calcium based stone and is vulnerable to acidic damage. This damage is more commonly called “etching.” You may be able to address minor etching using a marble polishing compound, but if the damage is deep or covers a large area it is best for you to have it professionally restored. We are experts at etch removal and would be happy to restore your marble to its original polished condition. If the issue turns out to be discoloration of a coating after all, you have an entirely different problem which we would need to see in order to address your concerns.