My Aquarium Plants Are Dying. The Question Is... What Is Causing It?

Plants need CO2, so, go out and purchase a CO2 reactor. This will help. Keep up the water changes, make sure there is not too much water flow, and lastly, keep the water oxygenated!! Use bubble wands, or air stones. I have had a planted freshwater aquarium for 5 years. Ohh, almost forgot, add plant food supplements. You can get all this at Petsmart, or Petco. Good luck!!