What development method did you use? If tray, it may have been that the first image received uneven action from the developer, especially if you did a stand/lengthy development. It may also have gotten stuck to the bottom of the tray, or another sheet of film. Fortunately, the other two didn't seem to be affected!
I wonder if there was a little developer that splashed onto the film guide. That would maybe explain some of the chemical stains? Or if maybe some of the channels got two sheets of film (that then stuck together), rather than just one sheet at a time. You might practice loading in daylight with some junk film, just to check your technique.
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