Man that sucks. Yeah you gotta vet these editors hard before you pay them. Ask for samples of their actual notes first, not just a list of books they worked on. A good editor will give you like a full page of feedback minimum for that price. Also check if they specialize in your genre cause a romance editor won't do much for a sci-fi story.

Did you mess with the exposure compensation slider too or just the ISO?

Have you tried using a spray bottle to mist the dust down before it floats around?