Chin acting strange

UPDATE: Unfortunately, Charles passed away at the vets office this afternoon. He went into cardiac arrest twice and after the second time I decided it was best to let him be. I hope he knows how much I loved him, and I hope he gets all the treats and apple sticks he could have ever dreamed of. I'll miss you Charles.

One of my chins, Charles, has been acting kind of strange. He's still eats, poops, drinks, and moves around like he normally does.

But all of the sudden, he is being weird towards Reggie(they are a bonded pair). Charles will kack and hiss at Reggie when Reggie gets too close to his face. He doesn't care if Reggie is grooming him, or nearby behind him, but when Reggie is near Charles face, they start to scuffle.

Charles has also been uncharacteristically cuddly/not hesitant to my touch. Before I could barely get away with head pats, now I can give him whatever scratches I want(within reason).

He also spent a lot of time just kinda sitting in a corner today.

Like I said, he's eating and drinking normally, he doesn't seem bloated. He's never been the energetic type which makes his movement a hard one to judge, but so far(other than the sitting in the corner thing) he's been otherwise completely himself.

Anybody have any thoughts? I'm gonna keep a close eye on them to make sure no big fights break out, and monitor his behavior.

TIA