Bkiggy,
Have you ever tested your Phosphate level? People in here have said It can be an issue with algae also. Rivercats, Aqua-chem, what's your feelings about Phosphates? OS.
I actually run a higher phosphate tank. At least 1.5ppm which helps in coloring up my non-green plants, which I have a ton of. I dose for very specific levels in my tanks in correlation to the types of plants I keep. I also keep nitrate at it's lowest safe level which is 10ppm. Again because of the type of plants I keep. IMO testing phosphates is just as important as testing for nitrates in a planted tank.