Having seen the scans, I now agree with Nige; the marks around the film sprockets look like light leaks to me. I've seen this sort of thing when I've accidentally opened my camera back with film loaded. If the film back is immediately closed again, some shots are completely ruined, while earlier shots are still OK, but dark marks just like those on some of your strips appear. I'm just a bit puzzled about why they'd appear where they do but not overlap significantly into the frames themselves for any frames (unless maybe some between frames 1 and 5 are completely dark).
If I'm right, I wouldn't worry about flaws in that part of the roll, at least not with respect to your film development technique. Instead, just shoot another roll and judge from it, or judge based on later frames that are beyond the problem area. Of course, you should be sure you don't repeat whatever caused the massive light leak when shooting subsequent rolls.