I agree with cull, if the whole bill is gone, then that means there is a high risk of infection that can get right into the bone in the skull. A cross beak and a ripped off beak are two totally different issues beyond being able to eat. Just because it does not look to be in pain, it is a bird, and birds are some of the best hiders of pain and discomfort till it's too late. One reason it is hard to catch any problems before they just "drop dead."
If you absolutely must keep them, take them to an avian vet where proper medical care can be taken such as ensuring no infections and sealing of any "open ends" that can lead to a systemic problem.
If you absolutely must keep them, take them to an avian vet where proper medical care can be taken such as ensuring no infections and sealing of any "open ends" that can lead to a systemic problem.