Canna PK 13-14 should be used at the start of the flowering, you're running auto so you should start at the 5th-6th with 0.5ml*L in each watering and increase in incrementals to 1.5 at the end (4 week period) then you stop using it till the end of the flowering.
I see you have the good hart and knowledge. Repect to you!!
But maybe you have wrong ffeding chart here is one like I've used in the past
https://www.littleshopofhydro.com/blogs/welcome-to-little-shop-of-hydro/canna-coco-feed-chart
same as if OP google
So yeah you would give it about week 4, during bulking up.
this is after stretch and before maturation, over ONE week period.
All the data are here, up to the OP the make is own research and decision.
That's it here for me =)
@sativaman, you can check the canna dosage and the proportion is what it is (0.5 to 1.5 in a 4 week period), if you combine products of different brands you should know what you are doing, he's using shogun vega&bloom, he don't really need a PK (I'm with you) but if he wanna use it, I would recommend to use in the lowest dosage and check how plant take it, 0.5 is the lowest amout canna say, he should use maybe a half of it and do incrementals, I think it is the best choice to avoid nute lockout & burn.
Using pk 13-14 from start to finish? I think you are confusing it with their CannaBoost other supplement.
>>(Just google their feeding chart if You are not sure for it)
Providing too muck P an K is a highway for nutes lockout, and ph rootzone fucked real good.