Lack of breast feathers on two of three 4 1/2 week old Canaries

I have two young Canaries which appear to have abnormal breast feather patterns (or lack thereof). One, which is the runt, is almost completely bare on its left side. The other has a bare patch on the upper right breast. The third has no visible defects and appears normal.
Is this a congenital defect? These are Red Factor Canaries.
The youngest is still being fed periodically by the father. I removed the hen thinking that she may be plucking them.