Hi
@Abducted! It looks like a Calcium deficiency. Either you somehow created a nutrient lockout by overdeeding, or your pH is below your expectations. In this scenario I would have decided to slow down on nutrients, make sure the pH-pen is perfectly calibrated, give some Cal/Mag in the next feedings and see how it goes after a few days. I'm glad to see you went through this issue, so keep up the good work and happy growing! 👊