Nitrates being sucked up

• pH:
• Temp:
• KH:6
• GH: 11
• NH4:
• NO2:
• NO3: 0
• PO4: 2
• Iron:
• Dosing: 15 mL Excel, 10 mL Flourish, 15 ppm NO3, 0.8 ppm PO4 morning, 15 ppm NO3 evening.
• NO3:PO4 Cumulative Dosing Ratio: 45:3.2 = 14
  

Notes:
This morning, there were more brown patches on the java fern, and the baby tears looked browner. Checked nitrates, it was zero already! I don't know why the nitrates are being used so quickly. I added 15 ppm NO3. This evening, I tested again: 2.5 ppm. Added another 15 ppm NO3. Perhaps it has something to do with all the extra angelfish fry in the tank. The plants have been looking greener (less red) lately as well.