Not any strict reasoning behind it but if i had to hazard a guess i would say they appear a bit on the young side, the younger ones always seem to have a certain look about them.
ive only got 1 male and 3 females, dont get me wrong id like them to breed but dont have the space for them. they get a mix of daphinia and blood worm every day... can hand feed all four of them whcih is quite amusing