Hell, we had all kinds of cr** in our water. We were constantly changing plumbing...in fact, I'm now a pretty good plumber.
Well drillers in this area have been hitting methane gas for years.
Anybody who also uses a water softener would have had at least rudimentary tests performed on their water to determine what the softener has to deal with, and county code doubtless requires health testing when a well is dug unless, maybe, it’s a very old one grandfathered in.
Anyhow, it’s theoretically possible the company f-ed up the aquifers and then went dancing la la la, but that sounds like an extremely foolish move on their part with Uncle Sam breathing down their necks all the time right or wrong.
If you first define intolerable levels of a substance to a very low level, then test old wells for those, of course you are going to come up with “poisonous water”. I part per billion of arsenic? O NO, we can’t drink that. They don’t tell you how many parts per billion of “poison” are in potatoes and other “healthy” vegetables and fruit