Could be a lack of magnesium. What did you use for crustacean meal and rock dust in your mix? What are you using for water?
It could be a lack of microbes in the soil, so the magnesium isn't available. How good were your worm castings or compost when I built your soil? Have you do anything to keep the microbes up, like top dressing compost or using EWC tea or some microbe product or anything?
Soil drying can cause issues in your root zone like pH swings, microbes going dormant or killing off roots, messing with nutrient absorption. How has your watering been?
Sometimes light intensity can mess with your leaves. What lights are you using, how hard are you pushing them and how far are the lights from the plants?