When you say, these are screen shots, what exactly are we looking at? Are they scans of the negatives? Or scans of the prints?
Either way, it strikes me that the pale spots seem slightly fuzzy, suggesting to me dust on something other than the negative
itself, e.g. in the scanner, or in the enlarger/negative carrier. The large dust spot in your post #4 looks distinctly sharper, making my point.
Other suggestions:
- Do you live in a hard water area? Commercial chemicals probably have Calgon incorporated to cater for this, but your rinse water doesn't. Using distilled water for a final rinse after washing can help.
- Another hazard is tiny insoluble particles, often iron. Do you have a filter on your water supply? It is really cheap and easy to fit an under-sink cartridge unit which will remove these particles.
- Do you filter your chemicals before use? It's good practice to filter them both into and out of the bottle. I use the standard Paterson filter funnels. It's amazing how much stuff gets trapped on the filter after a single use of the chemical, when you think it has spent all that time inside the developing tank...