Yes, it likely is a light leak, though the circular shape is a bit unusual. The most useful next step is to inspect the negatives and compare where the marks appear across the roll. If the same pattern repeats on consecutive frames or changes gradually as the roll progresses, that can help identify where the leak is coming from.

Things to check:

• Look at the negatives, not just the scans.
• See whether the streaks/circles appear in the same area on multiple frames.
• Note whether the effect fades or gets stronger across the roll.
• Compare frames shot at different times to see if it’s consistent.

That pattern information helps narrow down whether the problem is from the camera seals, back door, film handling, or possibly processing/scanning. Based on your description, a light leak is a reasonable suspicion, but the exact source isn’t clear from the scans alone.