Not on all plants? I think just 2? I’ve been removing leaves but I don’t wanna really remove anymore because they are autos and well into flower. Thank you
Looks like indented rust? Gold and silver in color? Weird! Doesn’t come off on my fingers.
I have 12 plants and this is only showing up on 2 of them as of now??
Most common cause is a calcium deficiency and usually from a pH issue.
Are you checking the pH in and out?
Soil should be 6.5 - 6.8 and Coco Coir should be 5.8
If pH is good then you may be need something with calcium. But first make sure the pH is good.
Appears to be a calcium deficiency and can be accompanied by a phosphorus deficiency as these 2 interact within the plant. With a phosphorus deficiency usually showing up in flower. Agree with @Spiney_norman most commonly related to PH being out of range 
Soil .and I always ph my water. I added cal mag today so I guess I’m on the right track. Thanks guys I’ll check back in a couple days with results 
U have late stage magnesium deficiency. Cal mag should fix it
Thank you
