Hi there. Looks like a cal mag deficiency. Also if your PH is out of range in the medium it could triger a cal mag deficiency to show to do lock out issues. Seems like your feedings are on point so I'd start with the PH of the soil. My organic plants grow best with soil pH of 5.8 - 6.8.
Also while your testing the PH might as well check your PPM to make sure it isn't getting out of range. At this stage my plants love it around 1100-1200 ppm. Hope this helps! ☺️