Pk booster? What else are you feeding your plant. What kinda soil and what week on flower are you in? Welcome to the farm.

put this way,i have a bucket of jacks classic hydroponic 5-12-26,it clearly states the fertilizer carries added boron,if added to anything other than intended crop or conditions can result in serious injuries to crops,that said i asume that the chemical break down wont fly in soil,same warning and added molybdenum which is also harmful for foragers .
so i would go with soil for soil products mate,it is your lungs or stomach ,you only have 1 of each