I have a 90 gal. Planted tank that I have started about 7 months ago. Going bigger. The past 2 months I have had brown algea on just about all my plants & starting on the glass where I do not clean as good. It is getting harder to get rid of. PH 7.1, NO3 0, GH 5, KH 2,. I do weekly water changes of 30gal. with RO top off. Any idea on how to get fid of this bad brown algea?