1st thing to cure the problem is to get your water chemistry fixed. you have not given us you fert regiment. you need to stick to doing this on a regular basis what ever you use liquid or dry.
bump up your co2 levels asap.
You must kill the BBA fixing the cause will not get rid of BBA
there are two ways to get rid of BBA a 72 hr complete black out which means cover the tank completely no light at all. This can work not a 100%. combine this with excel dosing with a syringe directly on to the BBA will cure it.
the other is to double dose for 14 days the recommended dose on the bottle will also cure it. (faster if you can dose this right on the BBA with a syringe)
after you cure the BBA cut your photo period down to 8hrs till you get the balance back off light co2 and fertz.
Good Luck BBA can be very frustraiting and hard to get rid of