The parents will feed the chicks with what they eat, and wean them to the same foods. You should be feeding a nutritionally balanced finch pellet or granule, not a loose seed mix. In addition, offer leafy greens, chopped veggies & fruits. An egg food is also important. You can offer a dry commercial egg food, or cook an egg with the shell washed, crushed and cooked with the egg. If you are only feeding seed, you need to add these foods right away. Typically you feed these foods year round, except the egg food which is only fed when you hang the nest each time. You should remove the nest as soon as the chicks leave it, then rest the parents for 4-6 months before returning the nest to them. The chicks need to be moved to a separate cage as soon as they are weaned, to prevent the parents from picking on them. You won’t be able to determine their sex for about 6 months, or possible earlier. You need to house them by gender if you plan to keep them, to prevent related birds from breeding. In captivity, they do not know any better.
Thank you for asking Lafeber,