@Carpman i had/have similar issue with you.
Initially, I spent over 3 months fighting with BBA. Dosed 20 - 30 ml of 6% H2O2 /day and Easy Carbo on alternative days with very little success.
The only solution it worked was to increase the flow by adding 2 Koralia Nano (1900l/h each) at both ends of the tank to increase the flow. I do have 1900l/h and 1250l/h filters in 320l long tank. Ph have been set to 6.1 on a controler 24/7.
15ml Seachem Excel spot dosing each morning with filters and wave makers completely stopped. 50% water change every week and filters are cleaned when i do the water change.
The lights have been reduced to 6h photo period. Dosing EI daily with Macro one end of the tank @ 7am and micro @ 11.59pm at the other end of the tank.
I can say, during the Excel dosing, no casualties. I do have shrimps snails, ottos, cardinals and gourami, none of them have been affected.
I did not trimmed any affected plants and did not increased water change, just kept a very rigorous maintenance schedule.
IMHO stable pH and increased flow was the key.
Most probably Easy Carbo will have similar effect. If the BBA change color from grey to purple/red ish, that means it's working. In 2-3 days it becomes white is and disappears. Most probably cleaning crew is looking after.
You can try to set the co2 to a medium level and leave it 24/7 for few days and observe the fish for any discomfort. Or if you can borrow a ph controller it would be better.
Zeus has a very interesting Co2 setup.
I hope it helps.