Start using PK13/14 when the buds are mainly developed but skinny - when they are almost joined up on the stems, but not fattened.
The PK13/14 will fatten them up.
Don't go in too heavy - at least half of the canna guide to start.
I Stop using it 2 weeks before harvest - about the same time i start my final cleanse.
Cheers and happy growing!