Certainly sounds like air bubbles to me.(posted 8980 days ago)Air bubble formation is an entire field of study in itself, but briefly: Air bubbles almost always form and stick at a "seed" site, either a small particle, a surface defect or chemical contamination. Check your developing reels very carefully for any scratches, dirt or water scale. If they're not obviously scratched, give them a good soaking in a strong solution of washing up liquid, with some white vinegar added if you live in a hard water area, and then give the grooves a good scrubbing with a soft toothbrush. After a thorough rinsing they should be good as new.