HELP!!! My aquatic plants are dying!!!!?

I'm not sure what to do. I don't know what they are because the plant was labeled with a big long scientific name. Basically, I got them Sunday, planted them in sand and added water conditioner. My plants are in my 2.5 gallon aquarium and I have a 10 watt flourescent light bulb that i leave on 10 hrs a day. The water conditioner had phosphate buffer in it which I learned later was bad for plants so I took out as much water as I could, 80-85%, refilled it with regular tap water and put in water conditioner (takes out heavy metals, chlorine, and chloroamines) that didn't contain phosphates. Now when I look at my plants, the leaves are turning brown. I don't know what is wrong or what to do.