I certainly second the suggestion to use filtered water at least. My pet Emperor Rosemary had died and it was very strange as temps and humidity levels were fine. Now that I've read your post, I remember that I have been using tap water from my lab to water her substrate (and her water dish), and the water was not safe for human consumption.
Rosemary could have died from something else but it's best to eliminate any variable that we can to prevent deaths.
But that being said though, I have been using filtered water and they still leave water stains on the sides of my Sterilite plastic containers and the massive chela of my Emps too. I do hope they aren't detrimental........worried about calcification effects.