why do you say that purple stems are cause by P deficiency?Ok my thought is you need to continue feeding with the bloom making sure your PH is correct You need to get another nute with higher PK ratios and start feeding that as well as foliar feeding that nute for those levels are too low in just your bloom. The plant will continue to use the N that is in excess and the purple will start to dissipate from the stems as you move forward.