although i would NEVER EVER actually recommend putting multiple plants into one pot, due to many reasons i was forced to do this during the grow im doing... im not having any major problems by anymeans and im flowering some beautiful girls.... check out my journal below in my signature if you want to check them out...
but as was said if you can re pot you should.. be careful when seperating the roots.. be as GENTLE as possible.. i would water with a transplant shock inhibiter/root growth stimulator... this will help your plants jump back sooner and help them start growing their new roots quicker...
good luck
sampson