You locked up your nutrients by using too much gypsum, oyster shell flour, cal-mag and other calcium sources, and maybe (tap water?). You are blocking the ionic cation exchange with too many hydroxyl ions. There's no room on the receptor sites for positively charged ions, so the plant is locked up so to speak. The lights maybe compounding the problem because the plant can't provide adequate protection for itself caused from the nutrient deficiency caused from the lock-out.