4x65 is a good amount of light. That is what I'm running over my emersed setup right now. Are you dosing other traces? This is my guess, and it could be wrong, but I am thinking CO2. Good levels? I say this only because in my emersed setup it is spreading like mad, growing faster than the HC, and the only reason I could think of would be that my plants can get CO2 straight from the air. Same tank, same amount of light, pretty much the same ferts.