My Wisteria also lasted for a couple months, can't remember exactly, but around 4-5 I think.
You willnot get this fixed without liquid fertilizer.
Holy cow. Now That's a planted tank.
Not sure what the GH of the water is, and the api root tabs alone were working pretty well for the past 3 months or so. The tank is 6' x 18" x 24"
This is due to a lack of nutrients. Wisteria (Hygrophila difformis) is a very fast-growing plant, and that means more light and higher level of nutrients
I'm not sure about the 8 (but less than $79)… I got my 4 there for about $48.