Probably would not add pk 13/14 until at least 3rd or 4th week of flower, first 2 weeks they transition from veg to flower. you wanna stay with more of a grow type nutrient formula. Then after flowers have developed which is usually around week 3 but this will vary depending on strain and environment, switch to more of a flowering formula.

Maybe for your case start pk 13/14 around week 3 and then add bloombastic around week 4 or 5 as your finisher.

I would alter nutrients during day 8-14 dependent on what strain your running. If your running a tall strain than you want to lower nitrogen and add the extra phosphorus and potassium. If your running indica's use it during week 3-4. But if it was me I wouldn't even add a pk booster, because all nutrients on the market have adequate amounts. If your in two separate systems, do a test one with and one without. Yield wise there will be no difference unless the manufacture is hiding other chemicals not printed on the label. If the pk source is an organic one, than there will be a difference in flavor, but the yield will be the same.