I would first try a new bulb with higher K rating around 6500K, bulbs at this color temp usually have a better mix of the different wavelengths, including more green. This produces a whiter light and will appear brighter. Sometimes these are available at Home Depot, Lowes, or similar, especially the 48", the 24" is less common so you may need to get one made specific for the aquarium trade. I use mostly Zoomed bulbs, they have one they call 'Ultra Sun' that is 6500K, I've also had a Coralife 6700K daylight that was good as well, Hagen Life glo 2 is another, though I have no personal experience with it.
One of any of these will be plenty for the java moss and anubias you mentioned as well as crypts, java fern, most swords, adding another fixture will increase the likelihood that you will have algae problems.