I would say thrips as well, Had them on my first tent grow BUT i was growing in store bought soil mix. My plants did spend some of their time outside in the sun so i dont know how or where they came in contact(my guess is the bag soil mix) I couldnt for the life of me ever find one on my plants(maybe they only come out at night lol)...but one day when i watered them i was looking closely at the soil for fungus gnats, and saw a bunch of these little bastards moving around in the wet soil..!!! Now with your grow medium..i dont know where they'd hide...or how you would go about treating them. i used safer's 3 in 1 and sprayed soil immediately after watering cause thats when they came to the surface. Good luck