Veg nutes

I'm Wondering if any grower with a little more experience would answer a question for me. What is the best water to use for a outdoor grow. RO, regular water from the spicket, purified water.. and also I understand that the plant needs food. So what is the best organic nute to add to the water for a veg state?

For billions of years plants have thrived growing outdoors with simple rain water, but Im sure they would have done just as good under the same circumstances but with tap water. Any liquid seaweed fertiliser is a good organic option for Cannabis growing in spring/early summer (veg)