Use gouache to create a Pointillist effect (optical blending) throughout your previously-made watercolor composition.
First, improve the original composition by consciously addressing more of the principles of art, then address Surface Quality, Texture, and Optical Mixing in the style of French Neo-Impressionist painter Georges Seurat.
Learn more about Pointillism and Seurat's concern with Optical Mixing in this Khan Academy video.
Your use of Pointillism and Optical Mixing should cover the whole surface of your painting.