Melting ludwigia and senegalensis

• pH:
• Temp:
• KH:
• GH:
• NH4:
• NO2:
• NO3:
• PO4:
• Iron:
• Dosing: 0.5 ppm iron chelate, 5 ppm Flourish potassium (+ 5 ppm Flourish potassium yesterday)
• NO3:PO4 Cumulative Dosing Ratio:

Notes:
I'm scratching my head as to what nutrient is deficient, some of ammania senegalensis and ludwigia peruensis have melted away, and some of the bottom leaves of the ludwigia repens had black spots/holes. The magenta is still just sort of hanging in there. I had added over 25 ppm of potassium at the beginning of the week, which should be planty. But because of the black spots on the older leaves of the repens, I'm guessing that there could possibly be some sort of potassium deficieny going on. I'm beginning to think that perhaps the UV sterilizer could somehow be causing some of the minerals (potassium???) to precipitate out of solution, as hinted at by the bluish cloudiness that shows up after I run the UV. It could be iron precipitating out. I only ran the UV for a day, and I dose iron every day, so I don't see how there would be a significant deficiency in iron, though.