Why is my finch poofy?

Try to give him/her water with a few drops of lemon. Feed it to him/her through a straw. Then mix gatorade with pediatric electrolydes in a gl and feed him/her that. You can buy the pediatric electrolydes at Walgreens. If you do not have a bottle of pediatric electrolydes, then just feed him/her gatorade every 20 or 30 minutes or so.