If you are supplying 10 hours a day of light that is enough; if you are supplying 6 hours worth a day that might not be enough for a light lover like hygro "angustifolia". H. polysperma also seems to prefer a lot of light, although it will live with a lot less than you are providing.

You might consider increasing the nitrate dosing. An average level of 5 ppm isn't very much for a tank with 3.5 watts per gallon. Some people suggest 10 to 20 PPM, or more.

Good luck!

Bill