Kinda look like developing spider mite larva. If you found them on the underside of your leaves and you see red dots (eyes) appear in a day or two that's your culprit.
I did find some of these little guys on my roots. Haven't been able to find out what they are yet. Looks like they have 8 Legs. Wondering if maybe they are nibbling on my roots cause my plants to struggle getting the right food.