Too much CO2 = Brown Algae?

Alright, I doubt that the subject of this thread is true, but I have an interesting puzzle to solve.

I have an extra 10 gallon tank I'm using to keep my extra stuff and try new plants. Currently it is jam-packed with anubias and some bolbitis. It currently has no substrate.

Due to an unusual setup, I am supplying way more CO2 than I actually need. I just checked my PH. It's at or below 6.0

10 Gallon tank
no fish
no substrate
anubias, bolbitis, willow moss
Lots of CO2 -- too much
PH <6.0
fert method: I'm doing Tom's estimative index. Lots of ferts, weekly water changes
KH: 6-8

MASSIVE amounts of brown algae. It's all over the leaves. All over the glass. I'm able to rub it off the leaves with my thumb, but it's just growing like mad. I would expect some if it is getting permanent / damaging the leaves. I don't want to ruin all of that anubias.

Soon I will have the equipment I need to better regulate the CO2. But I'm just curious if anyone has experienced anything like this before. What might the cause be? Too much CO2? Too low of PH?

Thanks!
Kevmo