What gave this? Light excess or nutrient burn or lack?

More than likley an over feed buddy. It can be very tricky to get the right balance I've had many grows when using un familiar nutrients where i get burt tips I usually just make sure i flush a tad bit longer as an overfeed can stunt a plant meaning it will finish later and if my thinking is correct it will also retain more nutrients. depending on your system and medium I'm going to gather soil or coco it can be quite hard to flush a plant as the soil will retain a lot of nutrients with hydroponics or coco its a bit easier and you can usually get rid of an excess in nutrients in a few days. Though burnt tips can indicate shes not got enough feed but i assume you would get other symptoms like yellowing bottom leaves and purpling of veins etc and i don't see any of that so i would say little bit too much :)