Mondo Grass maybe? Not true aquatic plant if it is....
I think so too. It doesn't look healthy at any rate, which is contributing to the extra dissolved organics as it decays.
I get so irritated at my LFS. I was there a few days ago to get some Prime and they have 5 plants for sale in their store, 4 of which are not aquatic. The only one that was aquatic was a horrid looking bunch of java ferns, holes in the leaves and completely covered with beard algae. Its no wonder people choose to buy the mondo grass, draceana, green hedge and bamboo, none of which can survive long-term submerged.
Looking at your photo again, it looks like the tank is situated between two windows. Even though there are blinds on the windows, they still will let in a lot of extra light. I'd also suggest either moving the tank so its not so close to windows, or putting a background on the back (and maybe sides) of the tank to block out light from entering.