Maybe more cloud layers. Increase the coverage of the current layer. Next make a new layer below it. In the density shader under the density tab is coverage adjust. This, with cloud density on the cloud's main shader gives great control.
The lighting/color for each layer can be altered by using the lighting tab controls.
Many posts don't recommend more than three cloud layers. I would not use more than four.
Oh, a low level cloud can be used in the valleys for fog. That may look good.