Check at seachem. Some plants melt with Excell/glut. They have a forum where you can post your plant list.
Seachem. Flourish Excel FAQ
"Q: I've been using Flourish Excel for the 4 days, and I've noticed that my Anacharis seems to be dying, while my other plants are doing fine. Why is this?
A: Anacharis is a particularly sensitive species (known to be sensitive to high temperature, trace copper, formaldehyde etc.). It is also sensitive to Flourish Excel. If you have Anacharis in an aquarium in which you are dosing Flourish Excel we recommend using Flourish Excel every other day rathter than daily"
(Friend of Bill W., One day at a time)