Cleaning fresh water tank

I'm intrigued.. Something just isn't right. You've flushed it out and have no problem with city water. And I assume by your posting water was OK before trip, so what happened must of happened on your trip. I would say keep flushing, but this might not be the usual flush and flush and flush some more. What color is discolored water? Has water pressure dropped in self contain mode? To find out more or what maybe in tank get a jar and catch some draining out and let it sit maybe 24 hours. See if whatever sinks to bottom or floats in a jar as in rust or very small rubber particles as in water pump insides getting chewed up or maybe even whatever stays mixed in with water. Maybe someone (child) was playing around and dumped something inside (dirt or whatever) but that would come out when you flushed. If someone started fueling up and stopped real quick you might be able to smeel it. Can you get a visual on your tank? One of our is blue color and hard to see. One is white and still can hardly really see.
Keep us posted. This has me interested.