Stop worrying so much. You're doing fine. Any clean water that is decent quality that you would drink is fine. I use plain tap water, letting it sit for a day before I put it in their dish. Most tap water or spring water has minerals in it too, such as calcium. Pinkies have much of the nutrients you would find in a reptile supplement. Personally, I don't use supplements if they'll eat a varied diet including whole fish and rodents. For a snake that only eats slugs or worms, a little supplement once a month is fine.