Well it might be septis. Or maybe a mag problem. I just Wana see what others think. See if we have the same thing on thoughts. It’s an auto so I don’t wanna go and do a defoliating when it’s gonna go into bloom soon. It’s the last one of its strain my late bloomer lol.
Could be the lighting but I can’t see what you’re looking at. Has colouration that kind of looks like a phosphorous deficiency but that could be the lights playing tricks in the photo.
I think if you step back and look at the whole plant it’s probably just some random plant spot. The edges of the leaves look to be mechanical damage. Do you have an oscillating fan on the plants?
Me personally I would try a tsp of epsom salt per gallon on next watering. Calcium shows up as spots, rust spots, grey spots, magnesium shows up like what you have, (not spots) Don’t look like you have a pH problems as you have no purple showing which happens if you go over 7.0 in your soil, so rule out pH. It takes many days watching new growth to see if you are on the right path unfortunately with soil, hope this helps some, happy growing !
You can also foliar with a 2% epson salts under and over the leaves with PH Water around lights out for faster absorption. Lights out is best time for the spray. Water drops could cause burn marks do to magnification from light. Good luck
Well i gave a lil calimagic. Ya 1 fan but to low for wind burn. Maybe some oils off my hand from touching it to much