Yellowing is normal for the leaf that you leave on a clipping.
As long as you spray the plants every day and keep the humidity in the dome high, most should root just fine.
I personally like to use 50ppm nute solution from day 1 (cutting) until day 7, even though at day 1 there isn't any root to absorb the nute, I like the nute solution to be there and ready when the first root nub starts taking in nutes, then I bump it up to 350ppm for a week, then 500 ppm for week 3 and 4. By week 4 they're ready to flip to 12/12.
I add about 5ml of weak nutes to each rapid rooter, then let it dry out (not all the way dry), then I add another 5ml to each rapid rooter. By Day 7 they should have tons of roots sticking out of the rapid rooter plug.