It probably would have been better if this thread was posted under planted tanks, but that is okay.
Root tabs and flourish tabs are buried into aquarium substrate and they release nutrients for live plants.
Fertilizers (often in liquid form, like Flourish comprehensive) provide extra nutrients in the water column to be soaked up by plants.
Aquariums naturally contain certain amounts of CO2 just like out atmosphere.
As for lighting something like this http://www.petco.com/product/111971/...cent-Bulb.aspx
(in the 6500K range) is what you would want to purchase to grow plants properly.
There could be various reasons the swords are dying off, but I am guessing it is a lack of lighting.