ok - that will not be a developer problem at all then. As the film info and details are clearly visible (as I assume you mean by the "edge markings")the developer has done its job as it should. it is definitely exposure problems in-camera. If it was a light leak or fogging from another source, and outside of camera, it would be a general fog or streak with no square edges etc.
It seems you have 3 frames where very strong light has exposed the film in the camera through the front (leaving the black square with defined edges). if it had entered through the back, it would be a more general fog as it would not have the benefit of the frame mask that the film sits behind in the camera. the rest of the frames have received no exposure at all - the developer had nothing to work on, and the fixer has washed away all the remaining silver in the film, leaving a clear piece of film.
it MUST be a shutter problem. Cut off my head and call me Susan if it isn't so (obscure Blackadder II quote circa 1984)