I see crust on your hydroton. You are going to need to pour clean water at pH 5.8 over the pebbles adn discard it, then change out your res and re-fill with magical or calmag until your PPM reads 250, then add your grow nutes up to about 400-600 total. THEN adjust the pH to 5.8.

Your pH is too high and your medium is showing salt buildup from somewhere. Plus your tap water is slightly soft, and we are seeing Ca deficiency and/or possible lockout from high pH.