The last 2 weeks I would cut the P and K part of the nutes to about 1/4 normal strength but keep the N and Ca part, and the iron, at normal strength. Most 2 parts have the N, Ca and iron in the A part so it's easy to do. Actually, some have part of the N in the B part so you would actually be cutting back some on the N too, but not as much as the P and K.
I base my suggestion on reading that N, Ca and iron are good for potency but P and K are bad for it. Haven't actually tried it yet though. I just read about that recently and got the idea. I will try it though.