Brown leaf tip.

Hello there don't worry to much that is very very mild damage I would next time you water collect some run off water from the bottom the pot and check the ph level your soil might be slightly to acidic making that happen If you do not have a ph problem then 100% it's you gave slightly to much nutrients prob nitrogen. Normally you see nitrogen affect the tips of leaves they get extra green or burn on the tip when to much. It's not a diffency you would see that in the veins of the leaves more I would water with only water next time you water and then after that return to the feed schedule ypu were useing maybe dial down the amount of nutrients you giving just slightly or switch to something with only p and k your close to harvest you could get away with starting to not give any more nutrients and let the plant ride it out till harvest with just water