I've had this 10gal tank for 6-7 months and my water wisteria is a NIGHTMARE! I got it when I started the tank, and it just randomly lost leaves and grew new ones on the top. It's mostly stopped doing that, but now the edges of the leaves are brown/black and it keeps losing them. There are still some healthy ones on the top though. Yesterday a big clump started floating around. My other plant (can't remember what it is, some kind of fern) is pretty good, one of the bigger leaves is brown but it's still growing and looks healthy otherwise. My substrate is gravel. What's wrong with the wisteria?