Yeah i would say that's an algae problem. I get a little bit of brown algae every 10 days or so in both my 6 and 10 gallon tanks. Mostly just on the glass, very little on the plants.
The thing I like about my Eclipse is that the substrate ferts seem to be supporting the plants enough for my taste. I have no ambition to do CO2.
I'm still learning the correct plants with the amount of light I have to work with. Don't feel bad, we all learn from doing things the wrong way first. Well, I know I do. I too am trying to figure out what I like and grows well before setting up my 55 I have been piecing together.