First off you definitely need a cleaning squad in there to help with that....otocinclus, Amano shrimp & some SAEs if you can find them. I would go with about 10 o-cats & 20 Amanos to start.
Second, what are you dosing, and how much? EI is not the method I would recommend with that lite of a plant load. I don't see any plants in there that a couple of root tabs, some trace ferts & maybe a little extra potassium wouldn't cover. I don't think you need to add any nitrogen or phosphate to your tank to be honest. Try that for a few weeks to see if it helps. Heck all ya' got to lose is algae at this point
