I'm sure the change in routine is part of it, but it's also possible that one of them got "into" something. If General was lounging on the sidewalk, he very well may have smelled something and rolled in it, as cats are wont to do. Just because you don't smell it doesn't mean Trouble doesn't. So, he could have some other cats' scents on him, and Trouble doesn't like that. If it's still going on for more than 24 hours, you may try bathing both of them (separately) ... though this may make them more irritable, especially if they hate baths as much as most cats do. (Some of my cats have not minded so much, and some have downright enjoyed baths, go figure.) I have had outdoor/indoor cats, and have seen this happen on more than one occasion. In my experience, either the scent goes away in a day or two, or the other cat gets used to it and/or figures out "ok, this is my buddy he just smells different". I hope G&T are back to being best of buds soon. God bless!