I've search this site, and other baking related sites, top to bottom and have yet to find a number, e.g., 3.6, or 4.2, or even a range of values of "correct" pH for mature sourdough starter. All I've found is imprecise (and a few ambiguous) references to "low" pH. That's as about precise as the three blind men examining an elephant. I've been brewing beer and making wine for years, and routinely check pH with a meter that reports a number. Simple.
Can anyone tell me the "proper range" of pH in a mature sourdough starter?