Statistically speaking, it is impossible for T304 stainless steel to rust all on its own. Because it takes decades of elemental erosion to rust surgical grade stainless steel.
However, this "rust" may be caused by material residue from food, oil, or the carbon found in hard water. Which can result in discoloration on the stainless steel surface.
The best way to get rid of it would be to clean it with an appropriately abrasive scouring pad and stainless steel cleaner. This will help remove the residue, buff the metal surface, and restore the shine.