Yellowing is not always a bad thing. The lower leaves can yellow when they start rooting since the plant is sucking nutes from the lower leaves to help grow roots.
In a couple of the pictures, I see those white "nubs" at the bottom. That does look like it's the start of the root mass. If the water is a little old, exchange that water with some clean room temperature water to give the nubs some new oxygen. Then put those back into the containers and see if the nubs are a little bigger in a couple of days.