Not enough light or nitrogen deficiency?
The LEDs are 8x3W LEDs, however I have no idea if each of the LED is indeed running at full 3W, probably not though.
The plants in the picture are sort of under direct light. Whereas the water sprite that is beginning to turn brown are quite shaded.
I am new with plants, so please bear with me. So when plants are blasted with too much light, and carbon supply can't keep up, plants would start melting? Especially from the bottom?