I brew with my best friend here in Annapolis, MD (although its a bit generous to give myself any credit), and he's been brewing at home since he was like 5 years old consistently. He's amazing and his beers are always very high quality. a little over half a year ago he started brewing at a local microbrewery/tap room. They had brewed before in the past but had fallen off, so they hired my friend as their head brewer. He's brewed several batches there, but almost all of them have turned out sour, which has never happened to him unintentionally before. To my knowledge, he's using the same brands of yeasts he's always used, but the equipment the he's using is different such as the brewing pot, the brite tanks, the kegs, and the equipment used to transfer them. The other big difference is that he is not using distilled water here; he is using tap water (and annapolis tap water isnt great, at least from my perspective as a Floridian) and he is using tap water because now that he's brewing on a larger scale, it would be far too expensive to buy jugs of distilled water from target in the amount that he would need for these large batches.
I know that the initial suggestion is going to be sterilization, but he has always been very great at sterilizing so I don't see how that could be consistently the problem here, when it never has been before.
I would like to know if yall have any ideas about the water, the equipment, or perhaps the transition from home brewing to professional brewing, and any related suggestions, I'd love to get y'all's input.

Thanks!