No! You'll introduce microorganisms that will just rot the cutting. When rooting in a non-sterile environment, you shouldn't add nutrients to the water. Low fertility encourages the initial root growth as well.

If they've started to grow roots at all, they're ready to pot up. The earlier the better, the less difficult the transition from "water-roots" to soil roots.

If you're worried about them wilting because the don't have enough roots, use a humidity dome or tent - essentially any plastic or glass container large enough to enclose the plant, reducing transpiration and water loss. Keep in bright shade until you see new growth.

Ok, thanks. I planted it. :)

It seemed like a good idea...I'm glad I asked!

I do that every year.
After I see the roots I pot them in potting soil and when the weather warms up I plant them out. Mine are growing right now in the garden. NEVER add soil to water.
Some people room them straight in potting soil, No pre rooting in water.