I have a problem with white spots on my negatives, it looks like dust, but when I inspeected negatives with magnifying glass they looked like salt crystals sticked on emulsion side rather than plain dust. I suspect that I may have fixer problem here. I use fresh fixer, mix all chemicals with demineralized water, and use all chemistry at recommended time and temperature. I use rapid fixer, wash film in running water for about 25 minutes, and do my final wash in demineralized water without wetting agent, and I never wipe the water off the film. Any clues? Thanks.