• I would remove one 65watt miday burst lamp from the setup.
• Leave PO4 at 0.5 - 2.0 .
• Raise Iron to about 0.5 - 1.5 .
• Lower GH to 4.0 - 8.0 .
• And without a doubt get an Automated Co2 setup to increase your levels to 20-30ppm.

I don't know how discuss can handle a 5 day blackout but I recommend that also. WC before & after. Uproot some plants and hand remove algae. Get some SAE's and Otto's. Also after the 5 day blackout I would decrease light to 8hrs and slowly increase to 10hrs as good results are detected.

55gal. w/ approx 40-50 Total water volume & 65watt X 4 bulbs == 5.2 watts per gallon for at least 5hrs per day, and all your dosed ferts ===> ..... well your gonna have to grow somthin!