Merged the two threads on the same topic...

Honestly your new growth looks damn good. The older stuff won't HEAL, but the yellowing should slow down as your pH stabilizes.

Okay, I have a question. Why did you choose the GH hardwater? What is the ppm of you tap water going IN? Where does your tap water come from (city, well, smaller municipal water supply, and if you know the water supply, what type of water body is it)? Basically what I am getting at is that you should know what exactly is making your water 'hard' if you want to use it to grow hydro successfully. Hopefully it is just dissolved limestone (CaCO3), because the plants love that. If you have high sodium levels, though, that could cause problems.
I've grown in hydroton using tap water but ran the Canna Aqua line instead. I like how it buffers nicely in the right range.
Another thing is, is this your first time bringing home clones and putting them in hydroton? The low leaves often look shitty early on. It's the NEW growth that matters, and yours is good. Don't freak out yet; I think you are pretty much out of the woods, just want to make sure you don't run into any other problems.