Thanks everyone for the responses. Some heartwarming, some hard to read but appreciate folks taking the time to give me ah honest response.
What makes it harder is that evevn though he's behaving different and sad, he is also behaving in part as himself. He asks for his food in the morning and evening, sometimes he eats it all, sometimes he has a couple of bites and then walks away. He still comes to my office and demands his treats like he has always done. He still sleeps with us. He's not hiding or withdrawing.