Hello. I got my cabomba a couple of weeks ago, and were full of color. But their new growth is now light yellow. They are not deformed or stringy, they just don't have much green. They are in a 5 gallon tank with two 13 watt fluorescent bulbs, a filter, and a heater. I do have a cheap DIY CO2 generator, and I have DIY Oscmocote Plus root tabs. Ammonia 0ppm, nitrites 0ppm, nitrates 80ppm, pH 7.8. Please help, I'd really like them to look good. I've attached a picture.