Are you using nutes? How long since your last flush? How far along is it? If I had to guess, I'd say over fertilization. Give it a good flush to leach all that crap out of the soil. Any one else have any ideas?
i use to see this on my leaves, every now and then but ever since i started using organic molasses it went away. i def think its a mag or phosphorus deficiency
Ok well i added some bat guano which is 10% phosphorus yesterday...But idk man seems like every crop i have something is always wrong with the leaves....
You can overnute by putting your plants into FFOF only, by the way. See it all the time. Cut it with some Happy Frog next time and maybe you won't see it.