I was also at Yosemite but more around August. However, I did get some nice shots of Vernal Falls. #1 is your best shot IMO. You can really blast that rainbow out of the photo if you boost up your saturation.
#2 is a little bland in terms of color. I like the way #3 shows the sun peaking through the trees. #4 could really benefit from some color saturation too. I think you could really bring out the green in the moss.
For your falls and other flowing water photos, you can try taking a longer exposure shot. Just lower your iso or tighten up your aperture so that you can expose the shot longer. This will help create that milky water effect and it looks rather pleasing.
Getting down from Vernal Falls was a bit scary, wasn't it? Those steps are so slippery from the sand and very steep!