Potassium or magnesium deficiency

• pH:
• Temp:
• KH:
• GH:
• NH4:
• NO2:
• NO3:
• PO4:
• Iron:
• Dosing: 5 mL Flourish, 0.5 ppm iron chelate, 25 mL Excel, 25 mL Melafix
• NO3:PO4 Cumulative Dosing Ratio:

Notes:
I can see over the past week or two that there are yellowing glosso leaves with pinholes developing. Same for the L. repens. Potassium or magnesium shortage?