Sally, if you have all three of them together, then one of the others is plucking this one because he cannot reach his neck to pull feathers out himself. The ones under wings and around feet, he can reach.
If you have not already done so, please take him to an Avian Vet for a checkup to check for infections because anytime birds are moved to new locations, their immune systems become compromised and illness can get a toe hold on them.
If you have him in cage with the others, please remove him to a cage of his own. We recommend caging all larger birds separately unless you have a huge flight cage with enough feeding/watering stations for all of them. A cage such as a double Macaw cage or larger would work for multiple greys. Keep in mind bar spacing needs to be appropriate for bird's size so they cannot get their head through bars and choke to death or pull their heads off in a panic.
Diet is also a consideration, and we recommend feeding high quality organic pellets like Harrisons which is Avian Vet endorsed. Here is a link on how to make the changeover as it does take some time and effort:
Before starting a change in diet, make sure all are healthy, and any that appear to have problems like the one you wrote in about, need to be examined by an Avian Vet. Climate changes and changes in type of cooling in a house can cause problems, and birds are always nervous and unsure in a new environment. Do not ever put any bird cages under or over or near any kind of air vents as this will chill them, even in the winter. A draft is a draft and can cause them to have upper respiratory infections leading to pneumonia. Also, birds need full spectrum lights above cages and out of reach. These can be found at Drs. Foster & Smith and are called Ott lights. There are also other brands, but you cannot find them in a home repair store or walmart as they only carry the colored lights, not the full spectrum ones. Light coming through a window is NOT full spectrum, and birds, reptiles and other caged animals have to have a source of full spectrum light to be able to grow, and stay healthy.
Let us know how all is going, and your birds will all need extra attention during this time of stress.
