What does " 0,0,0-.4 " indicate?
The string of numbers doesn't tell which is what or what it is.
Can you give more info? What do those numbers relate to, temp, lighting wattage, duration, etc.
UV will destroy the Excell. The chemical in the excell is an intermediary in the clorophyll carbon fixing chain. It isn't very stable at all.
If you're having to dose excell like mad... you have something else going on that needs to be addressed. There are a lot of brains here to help.