Right now is molting-time for all of them, my Green Cheek looks a mess right now, so does my Senegal...Looking at the photos it actually looks like he's been barbering himself for a while, so this isn't anything that just happened in the last week since you've brought him home...
At 8 months old he is coming up on the time for his big molting that will shed his baby feathers and grow-in his adult plumage, so he's going to be a mess for a while. You'll know when his first molt starts, because he'll be patchy and there will be feathers all over his cage and your house, lol. Once he gets through his first molt he should look pretty good, and you'll have had some time for him to settle-in to his new home and for you to also earn his trust and for him to feel comfortable and secure in his new home...In the meantime, make sure that he has many different types of toys to play with at all times (chewing toys, shredding toys, foraging activities, etc.) and that you're spending as much time as you can with him each day, so that he doesn't become bored or lonely and he keeps busy. It's good if you give them a job to do to keep them busy, something like giving him a paperback book that you hang-up in his cage to shred apart (they love that, I buy cheap, thick paperback novels and put a metal food skewer through them, and hang it inside of their cage, and start it off for them by ripping a page up so they get the idea, it will keep them busy for hours and hours). Also, hiding their food/treats inside of things and making them actively forage for it is another great way to keep them busy and keep their brains working.
