Athosanswered grow question 6 years ago Your pH is spot on for coco, your lights on temperature is a little low, but that will only cause slow growth, not spots, but try to up it to 24°C (75°F).
What you have there is excess P and or K, that in turn locks out other minor elements. Your feeding is too strong, dial it back to 1.0 EC (500 PPM) and only up it if you see deficiencies, when you put it to flower then up it slowly to 1.4 - 1.8 EC (700 to 900 PPM). Remember regarding feedings, less is more.