Jack's in RO comes to ~5.4, at least for me, this is a guess because I have always used the drops. For whatever reason it seems to work just fine. My runoff is normally between 7-8 for whatever reason that is. I don't ask questions and try to over think it if it's working great!
Ya makes sense, 5.4 will play. Trace is so available at that ph though that your gonna burn easier runoff ph being higher is inteeresting. Usually a hungry garden the runoff comes out higher. The plants are eating out the ph buffered nutes and you are closer to the starting ph of the water. Good for you man. I'm definitely not a runoff whisperer but I suspect that's a good thing.