Black spotting/dust in stainless steel utensils.Is this mildew?
The specks are corrosion pits. Austenitic stainless (aka- 18-8 , 304 , and several other numbers) are notorious for pitting in salt (halides). The 316 and 317 with molybdenum are more resistant but I doubt any cookware producer would go to the extra expense to use these alloys. However, I expect sitting for a couple days with salted water would be needed for pitting to develop. Out of curiosity, check it with a magnet; If strongly magnetic it is likely 13 Cr (410 SS) which would be likely to pit.