It may be that the older chick is begging louder and pushing the other one to the side when the parents feed. Or there could be a problem with the younger chick – something genetic, or an infection or something else. It may catch up or it might not survive. One option is to pull it and try handfeeding it. If you do this, then a trip to an Avian Vet would be a good idea. Or you can let nature take its course. But if it doesn’t make it, you still might have a vet run tests to rule out something the parents passed down to it. You can also have the parents checked out. Once both chicks have left the box, it is very important that you remove the nest box and rest the pair for 6 months. You should do this after every clutch whether the eggs hatch or not. It gives the hen time to recover from the strain on her body from laying eggs. The parents need to remain rested and healthy to keep producing healthy chicks.
Thank you for asking Lafeber,