I second those who say to upgrade the light. I tried growing plants with the original light and only low-light plants directly beneath the light would grow.. slowly. I added a AC20 and an Exoxotic Ecopico light and my tank has been thriving ever since.
IME the original filter/light combo is ok for a simple tank but to get good plant growth and filtration, you need to upgrade that stuff. This is what my tank looks like now (it's also got an HOB refugium these days)