WTF is this crap?

Check your DLI at the canopy. If it's just top leaves it could be to bright. Your lower leaves look ok so just ignore the ones that look like shit.

Looks like burning from a build up of nutrient salts in the substrate, most often the result from not watering with adequate run-off each and every time you irrigate. Also showing signs of nitrogen toxicity.........in other words, you are feeding too much or too often.....or both. You certainly shouldn't be using calcium nitrate with an NPK of 15-0-0 at this stage of the plants life cycle.

might be a combination

Looks like pH Fluctuation damage. Thats what the pattern looks like, but the colour of the necrosis looks like a rust colour which suggests Potassium deficiency

user error :P