It might be a light leak. If so, I can send you a kit + some instructions specifically for that camera to fix it for only $6...but before we decide that is what the trouble is, here are some important things to remember:
1) please remember the image is always "flipped" when imprinted onto the film. So, damage at the bottom of a developed picture took place at the top of the camera, right is left, etc.
2) light striking the back side of color film will make a damage mark that is yellowish, reddish or orange...every time.
3) light striking the front side of color film will make a damage mark that is grayish to white (exactly like an overexposed condition).
4) be careful to notice if the damage extends all the way to the end of the film...past the sprocket holes. If it doesn't, look first to a faulty shutter instead of a light leak.
5) the most common place a camera will leak light is at the hinge seal, followed by the long thin slots at the top and bottom of the film door, and lastly followed by the latch end.
Good luck...please let us know what your detective work reveals.
Best regards,
Jon Goodman