Poor Olivia!

Considering your in a small apartment I think the kittens did add too much stress to the whole place. Plus, you have been adding cats gradually over the last year and there is a limit to every cats tolerance.

This probably is a sign that their space is too limited & they need more room away from each other. I can't really tell you what to do Kelly, but it looks like a decision has to be made for the health of the household.