Little NO3/PO4 uptake

• pH:
• Temp:
• KH:
• GH:
• NH4:
• NO2:
• NO3: 10
• PO4: 1.25
• Iron:
• Dosing: 10 mL Flourish, 1 ppm iron chelate, 0.2 ppm PO4, 10 ppm Flourish potassium
• NO3:PO4 Cumulative Dosing Ratio: 15:1.8 = 8.3

Notes:
There's been little to no NO3/PO4 usage, it seems. Perhaps the extra hardness from the Ca/Mg is somehow preventing uptake of some other element(s). The only other element I could think of was potassium. Only approx. 9 ppm potassium was added since the water change (as part of the KNO3 dosing), so I added another 10 ppm to see if that would make a difference.