High, for the best results you should use 3 products, P booster during first month flowering and when the buds really start to swell you change from P booster to K booster together with Cal-Mag till flushing 1-2 weeks before harvest. Most people just use PK booster like PK 13/14 but it is not ideal. When you want the best for your plants you should give them the needed nutrients required for every phase of the grow. Enjoy your grow!