I would definitely take him to the vet, it is pretty serious when a rabbit loses that much weight! 1 lb is a quarter of his body weight!
Rabbits are very good at hiding their illnesses, so the fact that you are seeing such a drastic change in his behavior is very worrisome, and I wouldn't attribute it to just being old. My rabbit is turning 9 this year, and he has a consistent weight, eats anything and everything without hesitation, and is very active.
Didn't Archie have molar spurs/teeth issues? Make sure to check that out if he does. If his teeth are hurting him, that could be why he is losing weight and being a hesitant eater.
Rabbits are very good at hiding their illnesses, so the fact that you are seeing such a drastic change in his behavior is very worrisome, and I wouldn't attribute it to just being old. My rabbit is turning 9 this year, and he has a consistent weight, eats anything and everything without hesitation, and is very active.
Didn't Archie have molar spurs/teeth issues? Make sure to check that out if he does. If his teeth are hurting him, that could be why he is losing weight and being a hesitant eater.