is this a pest or an after effect of pests?? havent come across these before?

i seen a liitle scar tissue on some of leaves i had assumed it was dwn to me foliar feeding, but wit close inspection wit a mag glass i can see very sparsely populated litle black dots on underside that seem to be attached to the veins. that i think may be a larvae, has no legs or head and doesnt move at all. i mean there is like maybe 3 per leaf, also on the bigger leaves they seem to be long and thin like a thread of cotton if u like and again seem attached to the veins. not many maybe 1 or 2. a few weeks ago i sprayed wit a leaf wash twice jus to make sure it wasnt pests causing slow grwth as i grw in a shed. do u think i have a pest prob still or r they jus the left overs. like i said they dont move at all and i cant after hrs of research find any bugs that look similar, i have seen fungus nats before and can recognise most pests but these are beyond me any help appreciated

another prob i have found..
ok so i checked my run off and guess wat its around ph 8 my solution going in is ph6.2 so something fcked up there ,,,, also have spooteed some small black threads and dots under some of my leaves(minimal) i checked as there was some scar tissue on my leaves (as alraedy mentioned)


i propose gd flush through with ph 5.5 water with half strength nutes bleach out growroom and clean out gd. while flushing spray the fck outta leaves with some leaf wash that i have smc us com premium quality leaf wash,,, its has alreday been used once as aprecursor
if u think im going wrong way about it please post as i will be doing this this evening thnx all or if u have any other advise please stop by and light 1 up