possibly, the month that the film has been sitting around before finishing it, might be a contributing factor. On the other hand, film is usually rolled up fairly tightly so that humidity should not be able to get in between the film and its protective paper. Nevertheless, it looks like the paper has left its marks.
Have you checked the light seals of the camera? Seals can deteriorate with time, although older cameras used felt instead of the polyurethane seals, which get gooey after a few years. New seals might help to keep the climate out - if the inside can be kept or made dry before the film is inserted.