Some form of bug?

Hi this is my first post and I have been reading and learning a lot from all you guys . This is my first indoor grow and Im growing bag seed sativa in all purpose soil , harry carp, seasol, and now in flowering I have been using nirvana and bat guano pellets all are organic nutrients. Ok these plants are nearly 7 foot tall and are about 5 weeks into flower and have just started to look like something when I noticed leaves falling off the past week or so. Then leaves started curl down and under , so now I have taken pics of the fallen leaves and found some form of infestation. Under a magnifying glass I can see something but not sure of what it is and I see no webbing or any insects . Can someone please give me some advice on what I need to do?

Just as lights come on, quickly flip some leafs over and see if you find anything on the underside of the leafs, and take a pic of anything you find.
That really looks like bug shit or something, but I've never seen anything like that before.

Yea I was thinking the same, whatever it is its hurting my girls and there are four of them in the same condition. Im also worried about how many leaves are dropping. Ill check in the morning and see if there is any sign of insects underneath as I saw nothing when I looked earlier.

This morning I took pics when light went on and i looked under the magnifier but I found nothing.. Theflash has dulled it out but Ill load it anyway as you can see the damage to the plant in the back ground.

Looks like a fungus but .... I
Could be wrong though go get some lady bugs if you can lol they are bad ass predators I caught two and they are in my room as we speak chilling on the leafs getting high lol

Kinda looks like thrip damage but I can't be sure. Thrips can be hard to find somtimes, they are fast as hell. One pic looks almost like powdery mildew.

A couple of the pics look like it could be mites but others look like the spots on the leaves are too large. Whatever it is I would take it seriously.
If they are sativas and 5 weeks in the bud development makes me think they are going to be a 10+ week strain. You could apply some azamax as a foliar as well as do a neem soil drench with 3-5 ml per gallon. Maybe also pick up some spinosad and do a light spraying after 3 days from the azamax/neem drench 9(get it under the leaves). The gear will cost you about $50 but will be worth it if you have a pest problem.

Thanks for all the input guys, today I got home and had another really good look and I have found that many of the leaves have pin holes in them so it definitely is a parasite eating my plants and the way they are losing leaves if i dont stop it soon it will be buds with no leaves. Yea I reckon at least 10 weeks. These plants have been slow from the word go, always green and healthy but didnt show pre flowers till a normal indica would have just about been ready to harvest lol Im in Australia and lady bugs are around this time of the year but finding them could be a problem but I will try and ill get the gear if its available here to kill the suckers.
Any other ideas let me know. Thanks again..cheers,,,steovo