Good job finding bugs. Like I said, they can be small. That really didn't look like thrip damage though. You usually see what they call snot trails. A silvery threaded shading on the leaf surface.
It's possible they haven't been there very long though. It does look like bug damage to me, but I'm terrible at diagnosing nutrient problems other than the biggies.
If it's thrips or gnats or spider mites, spinosad and bt will attack them pretty quickly. You can be more aggressive if you are in veg, but I've had good luck with organic solutions as long as the bugs aren't bad. Alternate between treatments, spraying every 3 days for 2 weeks. Make sure to add it to your water so you get the soil and roots. You want to kill the adults and larvae, then catch the next hatch. You have to break the life cycle.
Thrips are pretty easy. Even spider mites can be dealt with. What you DON'T want to find are russet mites or root aphids.