you need to hit the plants with a pk spike at the stage your at i use big bud from advanced for 1 week along with my base nutes at week two of flowering.
then pk 13/14 at week 5 have you any grow shops near you,if you have tell them you want a pk spike or high phos,pattas feed just for a week then add it to your base nutes then back to base nutes after 5/7 days
Bump the ec up too,im not saying they look bad because they look on track doing well.
but get the most from em ya can leave em 9 week its the last 2 week when they will swell.
I'm not 100 % sure if the bud power is doing the same job has big bud whats it say on the tub the numbers eg 0-4-6