ebjd r usually smaller than regular jd's.
I would agree that it is over a month old.
Btw, I wouldnt put it with other aggressive fish, at least until it puts on more size and still even than I would make sure it has a significant size advantage over its tank mates.
Ebjd's are a natural color variant, but significantly genetically weaker than other dempseys, thats why breeders separate the ebjd frys into their own growout tank.
In my experience they also tank longer to heal.
good luck