If the spots are in exactly the same place on frames across all four rolls, the most likely cause is dirt or dust in the scanner optics during digitizing, not the camera.

On a film camera, the main optical cause would usually be dirt on the lens, but that typically changes in visibility and shape with aperture. If the marks stay consistent from frame to frame and roll to roll, that strongly points to the scanning setup.

A good next step is to ask the lab to inspect and clean the scanner optics and rescan a few frames. Also check the actual negatives when you get them: if the spots are not visible on the negatives, that confirms the problem happened during scanning rather than in-camera.