if you bottom out on nutrients (ie: if you have no nitrate) you can get algae growth. everything needs to be in balance.
is it green spot algae? do you have pics? you can get algae on slow groing leaves, and your dracaena could be called a slow groing leave in your tank
considering that its not a true aquatic plant. you should pull that one out and put it in a pot, try returning it or throw it away.
here is a table that explains what your co2 levels are in your tank
Tropica
it's kinda influenced by your kh and ph. if you really want to measure your co2 you should get a drop checker.