Also, if you dose a fair amount of PO4, this is typically from KH2PO4.
So extra K+ there.
I do not think we have that much limitation with K+ generally in planted tanks with EI, it's pretty much impossible to do.
If you adjust EI down to the 1/3 or lower ranges, have a low tech tank without CO2, maybe some Excel dosed tanks, or a large Discus/fish load, only then does it become possible.
Folks love a good correlation to assign cause when fiddling with their ferts.
Very rarely does it turn out to be the case. Water changes, when you last did a trim, then followed up with a good water change, trim methods, making a mess rescaping, cleaning filters, feeding fish etc, CO2, too much light, plants shading others too much. 101 things.
We cannot rule those out, but we can rule out K+ pretty easily.
At least those who do not have issues ATM(thus lack any "control" in any of their "test").
Socially, often the person posting is looking for "Me Too's" to confirm their belief, not knowledge and logic. That is problematic also. My ignorance and inability to grow plants is not equal to another's logic and good horticulture. Do we go looking for facts to support our belief, or see what facts there are, then try and draw some conclusion?
If several aquarist know they have high K+(dosing easily confirms this) and plant species X, Y or Z, plant health and growth is good, they have examples and pictures etc. You have to accept it their methods to quantify the the K+ seem sound.
Eg, if I dose 30-40ppm a week of K+, it's extremely unlikely I'll ever see a limitation for any plant species for K+. Plant health is excellent, plants are large, I sell plenty etc, won a contest or two, etc.
If you have a few folks like that, correlation may fix your issue, but the hypothesis that K+ limitation/excess is the root, that's dead in the water.
You have to let that idea go and try out a new hypothesis that caused your issues.
You will not learn from your mistakes otherwise.