Now on to the serious stuff.
If you're going to use a bottled spring water to ... lets say, dilute your must, it would be a good idea to have some sort of idea regarding the water's mineral content and alkalinity. Yeast likes and uses calcium for reproduction and it doesn't hurt to add a measured bit of nutrient containing yeast hulls and nitrogen to the mix.
Is there a water profile you can refer to that gives mineral content, pH, and alkalinity? If so, it's a good starting point toward understanding for additions of water to the must - and the same rule holds for making good beer better with the right water.