Mills Nutrients - Ultimate PKUltimate PK Gives You Bigger and Better Fruits Ultimate PK is a heavyweight PK booster that contains high levels of phosphorus and potassium two crucial macronutrients that are required in greater quantities during the bloom phase. When used in the last 2 4 weeks of the bloom cycle, this booster will enhance fruit quality and yield, while maintaining root health. How Ultimate PK Works Mills Ultimate PK uses clean and super soluble mineral salts, that