The tank is a 4x2x2 ft using 4 x36w PL lights. with co2 system. Had previously grown echinodorus when i just started this tank. After several rescape over the years decided to go back to planting echinodorus again. Realised that the growth rate is not what it used to be.
That is low light intensity, so that might be the reason for the slow growth. I know, with around 2 watts per gallon (240 watts for your tank) echinidorus varieties grow pretty fast and big, even with not so good fertilizing.