BBA won't subside

I've been having a BBA problem for a while. About a month ago, I took out all of the driftwood, boiled it, scraped it and put to back in the tank. The BBA is starting to grow all over it again. Of course there was still BBA on some plants an other parts of the tank that I didn't clean so not sure if it's just a case of it spreading again.

All of my water parameters are normal. I've tried dosing with excel and that doesn't seems to work. I run pressurized C02 using a PH monitor. Strangely I calibrate the monitor using 7.01 solution and the monitor reads 6.6 but when I test using a PH test it says it's around 7.0. I have 2 drop checkers in the tank and they are medium to light green. I run the lights 4 hours; on 3 1/2 hours off; 4 hours on using one 54 watt 6500K and 1 54 watt 650nm.

I've had a few fish die over the last couple of months so decided to stop dosing the Excel. Not sure what I should do at this time. Someone suggested taking the C02 off the monitor and just start running it an hour before the lights come on and the have it turn off she the lights go out.

BTW the tank is heavily planted and the plants are doing pretty well.

Any suggestions?

Thanks.