Within two weeks of you doing absolutely nothing, one day you will notice it all almost completely gone. The next day after that it will be beautifully clear.
They could be feasting off of the nutrients in your tap water. If you stop feeding them fresh water they will die off very rapidly after a while. Usually in less than two weeks. Doubtfully as long as three.
Bottled water is actually under less regulation than tap water in the USA. So...well I have no idea if "spring water" is better. That spring water may very well be just some tap water from somewhere else. It is a complete unknown.
Try it if you want to. But if you want to have some control over the situation just wait a couple of weeks. I promise that the fish will not completely fall apart because you skip a week or two on water changes. Unless the cycle is messed up in some way and ammonia levels are a factor.