Since you're growing in soil, chances are you have at least a few of those pain in the ass thrips......little gnat things. They don't really do much harm, other than the spots you have could be from their feces on the leaves acting just as if you had misted them.
I have had the very same problem, and the more I was able to control the thrips, the less spotting I saw. COPIOUS amounts of air flow at the plant base/top of soil is a good first step, as they just can't fly in and out of the soil with the constant breeze. Also placing the sticky fly/gnat traps throughout the grow, at upper AND lower levels will help even more.
If you have a small to average size grow, these measures alone should keep them under control enough to avoid using any type pesticide, or other topical treatment you may otherwise consider.....(just my $.02......but ask around and get some more input, I think you'll find they aren't as big a problem as they look.) They do look allot like spider mite spots, so be sure that's not what they are!!