Hi,
The foods you are offering are basically all treats, and the seeds are junk food. The bird isn’t thriving because he is malnourished. You should be weaning the chicks to a nutritionally balanced diet like pellets, or our foraging diets. Our foraging diets contain fresh, human grade seeds with the hulls removed, combined with other ingredients and all coated with a nutritionally balanced binder. Because we remove the hulls, the birds get complete nutrition with every bite versus a fortified see diet where the added nutrients are lost when the bird removes and discards the hull. You can also offer leafy greens, veggies, a small amount of fruit and a small amount of healthy human foods. Brown rice is OK, but it still doesn’t offer much in the way of nutrition. Eggs are OK for now while the chicks are weaning.
Weaned chicks should not still be with the parents or have access to them. At some point, the parents will either become aggressive with them, or will try to mate with them. You can never allow related birds to mate. If you can separate the chicks from the adults, the chicks should focus on self feeding and not beg to the parents.
This chick may have some type of crop or intestinal infection. I would take him to an Avian Vet to rule out an infection. An infection in the digestive track can cause excessive begging. Sometimes a chick will take longer to wean. But I think the main problem here is malnutrition which is causing the chick to feel hungry all of the time.
Thank you for asking Lafeber,
Brenda