I'm noticing this pattern on my corinto cucumbers grown indoors hydroponically. It's not on every plant in the system . I've looked under a digital microscope and can't find the villians but it looks like thrips to me because the damage seems to start right at the vien.

It could be thrips. It could also be a bacterial infection such as Angular Leaf spot caused by Pseudomonas syringae https://www.plantvillage.com/en/topic...

Have you any of the yellow sticky traps to monitor thrips as they move around. It maybe that they leave the leave before you manage to get it under the scope. See an example here http://www.bioworksinc.com/products/s...

Do please post close up pictures of the damage with your scope. That will help.

I don't think this is caused by thrips. There are none of the little black speckles you normally see with thrips, plus the necrotic (brown) patches do not look typical of insect feeding. It is quite an unusual and puzzling look- the pattern almost looks like a toxicity as if something was absorbed by the roots and translocated to the leaves.