Thanks folks for the information. I can't dose Excel daily in the summer, so I won't be dosing at all if I have to dose it daily.
I'll let the vallis settle in a bit more then... I was expecting that the cabomba would melt rather than the vallis, but they still look great! Kind of surprised by that, to be honest. I'll look into trimming it back in a day or so if it gets any worse. Thanks.