I see the word "perpetual" and have to say that you will begin to see problems with plants getting early exposure. Plants exposed to early and too high a P content will "yellow out". You will see reduced yields and quality with that problem! May take a cpl a weeks to get going but it will come on fast......after that.
I have such a hard time with the word "flush" as you never actually "flush" anything from the plant! In a solid media, you might "leech" most of the problem as in overage from the media BUT, in hydro, there is no such thing as "flush"...Only a reduction in available nutrient, and the plant reacts to that. Once a plant gets too much P....The damage is done and you can not "reverse" it.
You can slow it and sometimes stop it if caught fast enough. The use of a slightly higher N value can slow it.
Some nutrient lines use way high P&K levels and "hide" the P problem by raising N levels to delay the P overage from showing. It should be prudent to remind all, that N levels can be too high in bloom and can significantly reduce THC levels......
These products do NOT allow for reaching plant potentials in my book.....I could list a few but don't feel like a pissing match with those who swear by them......