Could fortified food worsen an enlarged and fatty liver due to their being synthetic vitamins in them?

Not due to vitamins: The foods one chooses may worsen one's fatty liver, but it would not be due to the foods' vitamins, regardless of whether or not the vitamins are natural or synthetic. One should avoid foods that have unusually large doses of vitamins in them, as there is generally no need to be eating unusually large doses of vitamins. Normal amounts of vitamins, as in enriched flour or fortified milk, are fine.