littlies Ive bred eat it pretty much straight after they start eating live food. Around 5-10days. Ive found once one has a munch and others see him eating, the others tend to investigate also. For those that didnt get on them straight away, I used a wooden skuer and pricked a small piece of chopped bokchoy or endive and waived it around their head and along the ground as if it was moving. They tend to watch it pretty intently thinking its alive and then grab it.
You'l find once they know what it is, and they can eat it, they generally will when you put it in. Also put a couple of bits close to where they are basking so they dont have to go far to eat it. Ive noticed sometimes if they have to travel to the other side ot the enclosure to get to it, they wont. But once they start eating it where they are, then their more interested to move for the rest
Just my experience any way. good luck
Cheers
Colby