Adult finches pulling out baby finch tail feathers

Question
We have 3 baby finches hatched 3 weeks ago today they left the nest and a few hours later I noticed the tail feathers on all 3 baby's were pulled out. I do not know if it was the mother, father or the 3rd adult finch in the cage. Is this normal and what should we do.

Thanks

Answer
Unfortunately, some parents do this. I don't know why but sometimes using a sour tasting spray available at pet stores helps. Otherwise you will have to either separate the babies from the parents and attempt handfeeding or wait until the babies are weaned and then separate them from their parents