Hi,
Stailess is a group of materials (NOT a specific material). Within this family there are several groups (won't bother you with the names).... These groups are very different in terms of their properties (including corrosion resistance). Cuttlery is often made with the cheapest Stainless steel (ferritic Stainless) which has low corrosion resistance). So they were corroded (oxidation is "dry corrosion"). You can use them, no danger (it's most probably an very thin layer of Oxides). Sure "appearance" is important, so either polish them (you received good answers how to do it) or buy new ones.
Best regards,