Remember, if the plants are deficient, they won't be able to photosynthesise as much light, which will make them more susceptible to excess light energy, which creates a stress loop. When I first started growing under LED I had a similar problem. The solution was not just to up the nutrient level, but to turn down the lights until they recovered. I discovered this after I removed one plant and put it in the shade outside. It recovered in the most part because it was no longer being light stressed and, once it had recovered, I put it back inside under LED, gave it a good feed, and it thrived once more.