If you're wanting to train them, one at a time is definitely easier!
Glad they're getting more comfortable with their surroundings! :thumbup:
They do look super tiny when they're not in their cage or on their playgym, don't they?
The food rationing system sounds good! Just remember you're going to have to eventually separate the seeds from the pellets anyway.
How cute! For stepping up, just continue like you have been for a while. Then you can try offering millet only if they get on your hand- take it away if they don't. Then slowly transition to one finger. That's how I got Niko to step up.