Many times BBA is related to poor c02. However it can also be exacerbated by the following:
1) Low N
2) Clogged/dirty/underperforming filters.
You can try a gentle excel bath for the worst infected moss to see if that works.
Mostly, I keep the best portions and fix the root cause(s).
Hard to say exactly the cause, but look at the whole tank and setup.
I would venture to say the DIY c02 is your culprit. Can you SLOWLY and carefully increase the c02 rate a bit? Turn up and observe for a few days to ensure the fish are okay.....
BBA is slow to recede and can take some time/effort. Have patience.