Good pics!

You will get better help if you fill out the troubleshooter's form.

http://boards.cannabis.com/plant-pro...anted-one.html

I'm not much of a grower, but I'll take a shot while we wait for one.

Looks like you have multiple problems here.
The first pic is definitely thrip damage, and yes when they bite through a leaf vein the rest of the leaf downstream dies.
You will find that the Thrips scoop out divots in the leaves, and that abets viral and bacterial infections as well.

I'm also going to guess that the PH has been/is low from the red petioles on those fans.
When was the last time you transplanted to a bigger pot?
When roots get crowded in coco the chemistry becomes unstable.

From watching my DWC grows, I learned that the roots will keep growing all through flowering, right 'til the end.
When growing in coco, I always up-pot when I flip.
Then at 4 weeks in, I "stack the" container for a little boost to fatten the buds with.

In your shoes, I'd fill a container with fresh, ferted, PH'ed, cal-magged, coco, cut the bottom off of the present container, and stack it.
The damaged fans won't get better of course, but the new growth will have a fighting chance.

As for the "Thrip larvae" in the runoff.
Is that a positive ID?
Thrips have 2 larval states and a flyer state.
The flyers bite.

Fungus gnat larvae are similar but the "flyers" are bigger and do not bite.
I don't know much about pest control, so once you have a positive ID, search the archives here for solutions.

Fill out and post the TF sticky and let's see what P.P. and the rest of the group makes of it.

Aloha,
Wee zard