The frames affected by this issue were 4, 7, and 10. I should mention that after trimming the leader long enough, and winding it onto the spool and shooting a few blanks, the first actual photo was Frame 5. So Frames 1, 2 and 3 were blank, Frame 4 was blank but was affected by this staining or light leak even though it was shot with the lens cap on. Frames 5 and 6 were perfect, Frame 7 was the one posted here at the top of the page, Frames 8 and 9 were perfect, and Frame 10 looked just like Frame 7 here. The stained or discolored areas look exactly the same on all three frames, and extend just a little into the blank areas between photos, but not into the next frame. The negatives just look like there's a dark shadow across those three frames (and a little beyond the edges) and its uniform on all three where it appears.
I should mention these are processed at my local full service lab. Its Ilford XP2, so it was done in the processing machine, which I assume means not loaded onto reels the old fashioned way?