NPK ratios high in Phosphorus are throwbacks to dirt farming. In the ground you need the high P because it washes out of the rootzone with every rain. In hydroponics you're just giving the plants way too much Phosphorus.
I know Homebrewer will call it BS because he hates all things Advanced Nutrients, but here's a link to a video about it:
http://www.growersunderground.com/blog/hydroponics-articles/the-great-phosphorus-myth-exposed
It's AN's website to take it for what it's worth, but the science is sound.