First off how many hours a day do you run your lighting? What kind of lighting and bulbs do you use? What is your WC
schedule and amount you change? Lastly what is your nitrate and phosphate readings?
Often leaving lighting on too long is a big part of the problem. For now you need to reduce your lighting to 6 hours a day. Also if you don't correct the problem causing the BBA it will just keep returning even if you spot treat it.
For spot treating you can use Excel or Hydrogen Peroxide 3%. Pull up 3ml of either for every 10 gallons of water. Turn off filters. Squirt the BBA slowly as close to it as you can get with the syringe. Wait 20 minutes and turn filters back on. If you have a lot you can treat an area a day. Usually within 24 hours the BBA will start turning white, pink, or red which means it's dying. It will come back if you don't fix the problem causing it.