Not sure if Bill has answered u but I’d wait! The build a flower has dry amendments already mixed into it so you don’t wanna overfed it! Takes too prob 7-10 days to start becoming available so def don’t wanna double up or u could wind up burning them and don’t exactly have a way to easily flush them boxes if need be!
If u haven’t done the build a flower yet then u could do a couple tablespoons of the craft blend below the BAF when u topdress it! Right as pistols are starting to make lil crowns u wanna have it topdressed for bloom!
Had to edit this cuz realized u said build a bloom! Don’t topdress and water it in with a nutrient solution unless the plants have deficiency! If not I’d just topdress and save the BAB til later in bloom in case they get hungry! Also I’d go build a flower next time especially in earthboxes!