New Grower Canna nutrients help

[colombiano]

So my canna pk13-14 finally arrive today. but i was wondering how long do i use this stuff for? ive been reading and their saying to use it 1s 3-4 weeks before harvest... is this correct? my girls have at least 4-5 weeks before harvest. any 1 here using canna or have. can you please advice me on how to use the canna pk-13-4 and canna Boost. witch arrive's tomorrow. I have using canna coco A+B and rhitzotonic mixed in a 20 ltr pot and feeding every time the coco gets drie witch is every 3-4 days