Planted tank not thriving but I think the NPK levels are reasonable
I'd like to get some help with my planted tank please. It's a 240l with Juwel LEDs and a 7 hour photo period. I'm injecting CO2 starting 2 hours before lights come on and cutting off 2 hours before the lights turn off. It's decently planted (I wouldn't say heavily planted) and it's stocked with approx 15 rainbowfish (bosmani, red, Kamaka). I last changed water and approx 10 days ago and added some Potassium fertilizer such that the NPK levels were 10ppm Nitrates, 2-5ppm PO4 and 15ppm K. The plants pearl everyday and the CO2 levels get to approx 30ppm at peak.
10 days on and levels are c.40ppm Nitrates, 2-5ppm PO4, 10-15ppm K. I am finding that my plants are growing well. My pygmy chain sword is growing runners but very slowly, Bacopa is showing little to no growth, amazon sword is growing new leaves but slowly, dwarf water lettuce is dying off slowly after turning yellow.
Can anyone suggest some possible reasons that my plants aren't thriving?