Update on great dane

So I posted a while back about my great dane chewing off his tail. He's fine now. His tail has healed on its own and he's eating almost half of his food now. There was on lady saying I had about excuse for everything and no its not like that, you're just not getting what I'm telling you. Anyways its not about that. My other great dane, jackson, he's 9 while duke is 13. I've noticed that jackson has been eating the same amount of food as duke. He usually eats all of his food. He's been about little down lately. I think his just worried about duke. When duke was 10 or 11 he ran away after chewing off the fence but we found him thank god. During that time Jackson was really upset because duke was gone but happy once we got him back. I'm afraid of how he will be when duke isn't with us anymors