If you have a magnifying glass or good zoom on your phone take some good pics of the two plants without moving them. Want to see if it’s bugs or damage.Yes, dry brown spots and it looks like the leaf beside it is starting to how a little as well.
You rub it or scrape it at all? I did something like that putting a SCROG net up once but otherwise can’t think what would do that over night without you knowing? Nute burn would not be on just one leaf unless you spilled.
@GNick55 i don’t want to hang him up with a bad diagnosis. You mind