Yellowing leaves on a CBD plant often get treated with more fertiliser when the real problem is that the root zone pH has drifted and the nutrients are already there but unavailable. Soil wants roughly 6.0 to 6.8 and coco closer to 5.8. The deficiency chart on https://calmcbdseeds.com (https://calmcbdseeds.com) pairs each visual symptom with the pH range where it usually shows up, which stopped me from overfeeding a plant that just needed a pH adjustment. A cheap pen tester pays for itself in one grow.