How's your pH? If you haven't already, check your run off and make sure your pH is where it should be and that you don't have a nutrient lockout going on. I see some red on the leaf stems which could either be genetic or a sign that phosphorus is being locked out. If the pH is good, then magnesium and calcium, so a cal/mag supplement or molasses and epsom salts. Those small red dots indicate a lack of calcium.