Sad to say, that is exactly what I got under the guise of an SAE. I
think I will have some strong words with one of the folks that works at
my LFS...

It appears that my doubling the dose of Flourish Excel in addition to
the CO2 injection and ferts for the plants seems to be working. Most of
the stuff has turned an orangish color and seems to be dying off.
There's some stubborn patches, but I'm rooting those out by hand for
the time being. I'll have to see if I can find a real SAE as an
additional measure if possible.

Thanks again for the advice!

-Kevin