Sorry I don't have an answer but more questions. I'm assuming RO is reverse osmosis, do you check PH of your RO water before you add it to your reservoir? Do you check again when it is mixed with
nutrients in your reservoir? just wondering because the nutrients I use have enough acid that they lower my PH. MY tap water is crazy high alkaline, over 9.0 PH, when I add enough nutrients it lowers my reservoir PH enough to acceptable hydroponic ranges. I try to use my A/C condensation water as much as possible but along with my nutrients, my PH gets in low 5 range and I have to add some tap water to raise PH. I have NFT system and only add water every other day when tankndrops below about 50 gallons.