There seems to be contradicting information when comparing to your other thread where it seemed you haven't been handling your chicks and were looking for advice: https://talkbudgies.com/budgie-breedi...ie-babies.html
The key in bonding with chicks as well as with older pet birds is to be gentle and understanding, to be able to read the bird's body language and to act according to it.
By not forcing
the chick/bird to do something against their will and to make a connection by showing empathy, by using our voices to communicate to them, by helping the weaning chicks to be self sufficient and by offering them food, by gently playing with them and by being consistent with training/taming, that's how one achieves success.
Are you sure the father budgie is truly plucking the chicks' feathers?
If all of your budgies are housed together, then the stressful situation may very well be leading to unnecessary aggression towards the chicks and this can certainly impact negatively the chicks' mental state, especially when they associate being picked up by you and getting a few feathers plucked as a result. They seem to not be in the best of environments where they can develop the confidence needed for the future challenges in life.
This can also impact their personalities and make them overall more nervous and anxious and less likely to be receptive in bonding with people.
Problems with aggression can also arise if these chicks aren't properly socialized, they can inherit the aggressiveness shown to them by their father.