Do you have a doser with an unused dosing pump? That'd be handy right about now.
Turkey basting the rock before each water change and gravel vacuuming the sand will help a lot in reducing nutrients. Do you have anything like bioballs, ceramic rings, sponges, etc in the sump? Do you have filter socks or filter pads? How often do you change them? How often do you feed the fish? What do they eat? How much do they get? Are you wet skimming or dry skimming? Which skimmer? (I'll go look if it's listed)