Yesterday was feed day both BC and BB#2 are getting 4.5 gm MC 5ml calmag per gallon.
If BB1 is burning then you may need to cut back the MC to 4.5g or 5g. The leaf margins look like a K def, which would more likely be a lockout than a def.BB#1 she's the fussy plant. Is getting 5.5gm MC 5ml calmag per gallon.