The pH was too high was was locking out certain nutrients from your plants.... now but just feeding them plain water they are going to lack even more nutrients than they need... I would get some half strength nutes in there asap also what kinds of nutes are you using and how are you mixing it? Also what are you using to adjust pH and how are you doing it? Also yes they do have a "gizmo" its called a TDS meter or PPM meter they have them on ebay u should be able to find one for cheap. Looks like you got ripped off already buying that poor excuse for a hydroponic system. YOu could have built one yourself by going to walmart for half the price and it would probably work better too. Also please stop calling it hydro juice its pissing me off lol... call it nutrients,nutes, nutrient solution or just refer to it as your res.