Test strips are only a little bit better than sticking your finger in the water, then in your mouth, and guessing what the readings are. I suggest that you get about $50 worth of test kits: Salifert Nitrate test kit, Salifert PO4, API GH/KH and a TDS meter.
For CO2: no good test kits exist at a reasonable price. Do the pH drop test: put some tank water in a glass, let it sit for a few days, then compare the pH to the tank water after CO2 has been on for a few hours. You have enough CO2 if you get a full one-point difference in pH.
I never understood how the envy provides the traces with their crazy formula, maybe it does. However, other than your fish, there is no NO3 or PO4 being dosed, both are critical macros, but we won't know how much you have until you can actually test for them. Report back when you do. Same for Mg and Ca, but given your RO and no apparent re-mineralization, you may be lacking in Ca, Mg and K ...all critical macros. Seachem Equilibrium-type products will address that.
Without sufficient CO2 and ferts, high lighting can over-drive your plants, making them unhealthy, then algae can thrive. follow @Maryland Guppy
's advice on getting some PAR estimates at the substrate.