This is very normal and happens year round for the white down. The colored feathers follow more of a cycle often in the last spring and again in the fall sometimes heavier some seasons than others and usually if they lose a feather on one side of their body, they will shortly after lose the opposing feather on the other side to keep them aerodynamic. The feathers then grow in looking like a pincushion and they pick away the keratin sheath. Sometimes they get a little grumpy during this time as I am sure it is uncomfortable. If they are a single bird like mine, she appreciates when I try to break up the the pins on her head that she cannot reach. It leaves a little more dust during this time. If she is on my shoulder, it will look like dandruff. Very normal.