Burnt and purple fan leaves

coco has no nutes, so you must fertilize every time... with 10% runoff to avoid buildup due to choice of concentration. that doesn't mean concentration isn't too high and will build up in plant. this is where observing and adjusting formulat comes into the equation. it's somethign you learn over time. so, correct the formula imbalance using a leaf symptom chart.. take notes. stage in life cycle is important to consider as well as season -- someplaces have drastically different VPD depending on time of year you are growing and that impacts how fast the plant drinks. the purple/red is either genetics or colder temps at night below 68F or so. it doesn't take much. they are "Fall" colors for the same reason leaves change colors outside on trees and such. you'll be fine, but cutting of all fertilization was the wrong choice. you may have need to adjust something, but ceasing providing building blocks to a plant will only hinder growth. conservation of mass applies.. it cannot manifest NPK/CaMgS elements from nothing.