Your right organics and a ec meter is a waste. But as a newb doing hydro it would be my advice to run a sterile rez. That could be very bad advice as I have not really researched teas at all. I have a bit more experience with soil though, first grow ever was 39 years ago (god I'm old lol). I over the years I have read countless books, articles, etc. yes it helps grasp the fundamentals of growing but experience is king. Two runs is hardly enough time to understand what plants need imo. Also not being rude but your grows seem to be a bit smallish, but nice and healthy, perhaps some tweaking is in order to maximize your system. I struggle with identifying problems and always will I fear. Keeping track of ph and nute levels is, again imo, the best and I dare say, the only way to understand the plants needs in a hydro set up for newbs. But to OP, just get her going. Follow the basics and tweak things to suit your needs, keep things on the weak end of the scale re nutes, monitor the Ph, change the res as needed (monitoring water will help), and keep the res cool. You'll be good! Also pick a proven, easy to grow, potent strain (dont want to grow shit lol), may I suggest White Russian or some other long running, stable strain. Again good luck with your setup and keep us updated.