Slight case of nute burn. Nothing much to worry about unless it spreads to other leaves higher up on the plant. Just back off on adding any nutes for a couple of days.
i agree with thatI don't think you can go out in the yard and find a plant with perfect leaves top to bottom. It's natual for the leaves to show any amount of stress. It can also happen when you pour the nutes in the system. If one root takes too big a drink at the wrong time it will show up on a leaf. Your problems are very minor and should not be overreacted to.