What are you trying to make sense of? Why, when lights/CO2 were turned off, you got thread algae and BBA? Assuming it's that, I'd guess that the algae was just a bit more efficient at soaking up nutrients left in the water column, while the plants "shut down" (at least more than the algae) due to CO2 and/or light limitation. Just my guess...it could be off base.
Regarding the Excel, I'd recommend trying spot treating if you've had bad experiences with the 'full' overdose approach. Just spot treat different areas on different days...and it'll work better if you can shut down your filter for a few minutes during the spot treating.