Just this leaf and one other one that's not as bad on a different branch. I was also doing a bit of research and came across 'Iron Deficiency' that looked quite similar and heard that the cause could be PH related, but my other plant that I'm growing alongside it is fine and I always make sure my PH is between 6.0 - 6.8, so it's making me question whether it could be some other issue..Idiopathic Lateral Interveinal Chlorosis.
In all seriousness though, I'm not sure. Will bump your thread though and see if someone else has a guess.
As a shot in the dark, maybe start of iron deficiency? Is it limited to just that one leaf? Anything else going on?
BioBizz All-Mix SoilWhat are you growing in coco