I feed my youngest ones weekly though the male I'm going to push out to every ten days when he turns three years old this summer. The oldest female gets a large-ish small rat or a small-ish medium rat every two weeks.
Don't get too hung up on pictures if they're babies unless you're assessing their overall condition; due to the color change they'll look different in six months anyway.
Obviously they'll need to be QT'ed for at least three months if they're coming from a pet store, these guys can get hit with all of the diseases that affect other boids.