Who Do I seclude?

Ok I need advice please. As some might know I have gotten a new kitten Fez. Fez has a URI, he has been on antibotics for about 10 days now and is getting better. My other kitten Stash is showing signs of having a URI too, he has been snezzing a little and had nose discharge lastnight. Other then that Stash has been acting normal, very playful, etc. I'm gonna take Stash to the Vet tomorow since today is Sunday and they ar not open. I'm not sure which one of the kittens I should put in there own room. Since Fez is on the mend should I let him have free roam of the house, and seclude Stash since he is just begining to show symptoms? Since Fez is so skinny and weak I dont want Stash's sickness compremizing him. I need Fez to get better so he can start putting on wieght. So who should I seclude? I'm thinking Stash b/c if he does have a URI he will be sick for about 2 weeks, give or take, and Fez should be back to normal in a couple days. But Im not sure, so help!! Thanks!

 

I would put the one who hasn't been on antibiotics into isolation.