When scanning old color negatives (37 years old) I get what appears to be an overlay on some negatives. The problem is more visible in dark areas (clear on negative), but is also in the light areas (dark on negative). Could this be some form of fungus growing on the film? Anyone have any suggestions on how to remove it? On some images I also get areas where reddish color appears in dark areas of the image. Both of these are visible on the attached image.