mmmm I'd go easy on fruit, especially depending on their age, and then they'd need grit. How old are they? When they're out with a mama chick, they start to peck up things really young, including grit but you can get some parakeet/canary grit from the pet store for em. They need bacteria in their gut too, so give em some small amounts of PLAIN unsweetened yogurt in a little dish for a few days, keeping an eye on their fecal matter though they have great little digestive systems.
After a few days of that, they love bananas! they also like slaughtering little apple slices, but apple seeds are poisonous!!! So NO seeds!!