Get ready - stupid plant questions coming. Do I shut the HOB filter off when dosing with Flourish Excel? The plants I have are anubias, watersprite, pennywort and cabomba. All are doing very well but a couple of leaves (at the base) of the pennywort turned brown and died. Is that normal for this plant? The top of the plant is doing great, and the other plants are as well. I don't have any fish in the tank yet, but am assuming that the Flourish Excel won't effect them in any way?