Are these homes on a comunity well, or, individual wells?
Individual wells may vary.
The grounding may be a factor.
You are facing a problem that is difficult to find the exact problem and cure.
There may be several individual problems adding up into a combination problem.
There is a lot of information here on copperpipe corrosion for your reading pleasure.
You are asking the right questions and looking in the right areas.
Good luck on finding your cure.
In some cases (many) it is far easier just to repipe using a material such as PEX or CPVC.