Root aphids maybe? I do t use them but there is many like this on Google and here
2 weeks till harvest found these little things in autopot water
Just doing a check up in the tent plants seem as healthy as can be but I just found a load of these in every pot have also found them in my vegging cuboard the other day on my other 5 plants .. I been using tanlin on the ones in veg paranoid about gnats but they don't seem big enough for nat...www.rollitup.org
Coming out in the runoff? My guess is springtails.