Unfortunately I don't know if he's plucking or not. Are the feathers coming from the front chest area only, if its from the chest only then this would suggest the bird is plucking.
Is it a time your grey might be starting a moult?
Where do you live? Is it cold and the furnace or heating is on high lately? Could your grey be experiencing dryness from the heating?
Do you let the bird shower daily? Or do you mist him so he can obtain moisture on his flesh under the feathers?
Have you been feeding him a new seed diet or any new fruits or veggies lately that he's never had before? Sometimes a change in diet can cause feather issues.
Most of all has the bird been under stress recently, have you been spending as much quality time with him as you usually or always do? Sometimes birds get emotional and can feel a little neglected when we get busy and might be spending less time with them.
Spoil him and spend extra time with him so he feels you aren't ignoring him.
If you find the feather loss gets worse I would take the bird to an avian for a check up.
There's a bunch of suggestions for you here. Please let us know how things go with him, I really hope he's not plucking.