I remain skeptical that you'll see much, if any, corrosion effect from virtually any household water (softened, unsoftened, RO, ...) in cleaning a brass instrument. You just don't clean it that often (even if you clean it every couple of months), and each cleaning doesn't leave the water in contact with the brass for long (maybe a half hour?). The image in all these doomsday scenarios requires conjuring up an image where the water is actively affecting the brass while in contact with it and basically eating it away via chemical activity. Given the actual circumstances, that seems pretty fanciful and far-fetched. Maybe if you fill the instrument with the water and let it sit for a few days at a time, then MAYBE you'd see such corrosion over quite a long period of time and cleanings. Or maybe if your water has the salt level of sea water (which will corrode things pretty quickly -- in a matter of hours if left unflushed) -- although remember that brass is the traditional material for fittings on boats and ships. But my experience of seeing what happens to copper pipes (with softened water, and unsoftened water) over DECADES makes it difficult for me to buy into the hypothesis that cleaning an instrument a number of times has resulted in "red rot" or anything similar. The interior of the instrument remains in constant contact MUCH longer, over much longer periods, with the combination of condensation from the player's breath and saliva.

Aside from minor (verdigris) oxidation -- which is very common with brass in virtually any circumstances -- the only time I've seen anything approaching the sort of chemical effects being discussed was when I filled up a horn with full-strength vinegar and left it over night in order to remove any calcium deposits. This DID have some results in terms of leaching. But they weren't visible to the naked eye and were evident only in how smoothly the tuning slides functioned. This was not the smartest thing I've ever done. And vinegar has a pH of less than 2.5!

In addition, it seems to me that the original description of the appearance and history of the "red dots" is more consistent with a flaw in finishing (buffing, degreasing, lacquer application) than with chemical reaction from the inside. But maybe that's just me.

So my view remains (and I could be wrong) that if you're seeing peculiar spots in the finish of your horn or in the interior, the first thing to do is to take that issue to the manufacturer. Of course, there's always the chance that there's something you're adding to the water as part of the cleaning process that might be responsible, but I can only report that I've used some pretty strong solvents and degreasers (I don't do it regularly) and not seen any obvious effects from that -- except a cleaner horn. I'm really interested in what Adams has to say about the problem. Everyone runs into manufacturing problems and failures at one time or another.