Water quality is something John Kempf brought to my attention a couple of years ago. I’ve deliberated on it for awhile, and what John says makes sense, especially for seedlings and foliars.

I’ve also found other references (although they also partially reference John, so circular logic abounds)

https://growabundant.com/foliar-feeding/,

https://growabundant.com/bicarbonates-in-irrigation-water/

Water is the single largest ‘amendment’ added to seedlings, who obviously don’t have much of a soil buffer. Even putting mineral content of water aside, constantly dosing potting media with high PH water seems, less than ideal… I am going with a cheap 600 GPD model (from Amazon) and storage tanks to start, and will observe as best I can how much of a difference it makes. I’m concerned that RO water on it’s own will strip nutrients out of potting media.