The poor dears look thirsty! Especially with the very low humidity, a drink will cheer them up.
6.4 is very slightly too low.
Also, switch to tap water unless you have a compelling reason not to.
I like PureBlend Pro. It's a fairly forgiving nute and IMO better quality than the FoxFarm. There's a Botanicare product (TriFlex) that is equivalent to the FoxFarm if you want to go the cheap route with a 3-part nute. But I like the PureBlend Pro a lot. Bonus, it's loaded up with good organics that help buffer pH.