#1 Too much out of focus stuff and other stuff that is in focus but not interesting in front of the water fall.
#2 Not much different from hundreds of other water fall images. You might try framing it with the falls to the left, so the outfall has some place to go.
#3 The aquamarine water makes this quite distinctive. I wonder how it would look with different shutter speeds.
#4 This one has multiple focal points at different distances. I like that. The eye meanders with the water. The green moss contributes to the composition. You might try cropping a bit of the foreground, which I don't think adds to the image.