When did you get your new rat? Did you quarantine
her? Either way, all your rats appear to have been
in contact with each other so it's done.
Your other rats are probably messing with the new one,
there is a whole heirarchy among rats (as all animals), and an introduction process you should follow. Following is a link to read that will be helpful.
Please be careful, watch to make sure the new one
does not get hurt.
Introductions take time and patience - please read
this link, and good luck you:
http://www.ratfanclub.org/newrat.html