Pk13/14

just wondering what eveyones opinion on pk13/14 is.
what are your routines n when do "you" add it to your rez.?

only reason im asking this is because ive read that sum only add it once and sum add all the way thru.. quite a mixed opinion
personally i usually add pk from 4th week till 7th week.
is there any benifits from adding pk right from the start , or from wk 2 of flower.?

from week 3 til 1 week before chop, 1-1.5 ml per litre, heard hammerhead 4-8 is better

thanx del , will be good to see what differences there are amongst growers.