What a lousy situation. I am so sorry there is trouble in "paradise".

This is what I would do (and it is only my opinion).

Take Chipper to the vet. It just sounds like something is bothering him and the other cats are picking up on it.

Place Nugget back into a room (like when he first came) and try to "retrain" him to use the litter box. And then maybe try adding another litter box somewhere, maybe one that is a little larger.


You may also like to try a feliway plug-in or two.

Good luck figuring this out.

{{{{{HUGS}}}}