I'm not a hydro guy, but in soil high nitrogen and high ph can cause ramshorning, but it looks more like the "claw" to me. In hydro I believe 6.0 ph is a tad high.
How tan are the roots? Often the nutrients can stain the roots tan, but brown is a bad sign. Any bad smells? (algae perhaps?) Did you wash your hands before ripping the roots apart?

Someone else with hydro experience is going to have to come in and verify or correct anything I've just posted though. I'm ok at soil grows, but hydro is a foreign language.