Ttis depends on how you currently feed. the idea is to maintaina healthy concentration in the substrate and the plant does the rest.
studies show amping up p and k does nothing for yield or potency. There's a happy zone that allows the plant to meet its potential then there is the toxic nonsense of blasting the shit out of the plant with P/K.
Read and react to the plant... you can test boundaries but be systematic and patient. e.g. this cycle test a bit more P and see if you run into a toxicity... a toxicty explicitly tells you that you provided too much (whether over 1 week or 2 months will indicate severity) and should be able to extrapolate an equivalent reaction for any deficiency seen. Once you got that hammered out, do the same with K or anything else...
it's not that simple of course... many of the nutrient molecules have 'relationships' with others... some can inhibit the availability of others.. raising some may need a bump to other stuff -- See mulder's chart for a rundown on that stuff. point is if you shift one, you may need small adjustments to others but the plant will dictate.
There are slightly different needs in flower than vege. so you just repeat the process for vege and flower.
i feed the same amount of p and k, give or take small variance, and i don't run into deficiencies nor toxicities involving P or K. So, kinda hard to say they don't need similar amounts in both vevge and flower, otherwise i'd be running into a shit load of problems all the time.
So, it depends on how much you currently provide. Plus, you are in soil, god knows what kind of delayed release is ongoing given ingredients to typical soil fertilizers. the potential lag between providign it and when the microbes break it down for the roots is another thing to consider.
you can't increase bud size by force-feeding a plant. the genetics dictate whether it can form huge colas or not. The best you can do is simply keep the plant happy and provide a conducive environment to growth. there's no magic product that can "boost" bud size despte all the nonsense marketing bullshit out there. They are simply lying to people.
DLI + other parts of environment and a well-balanced diet is all you can do. the well-balanced diet will be dicated by the plant with simply observation and systematic adjustments to your formula over time until you find something that works well 90-95% of the time. these plants are perceive to be picky, but that's more a result of esoteric, poorly balanced fertilizer regimens predicated on marketing nonsense that preys upon the hubris of growers.