Those plants are to far along to seperate them now.
Idealy each plant needs its own pot. 3-5 gallons is best.

I wouldn't seperate those plants now, the roots will be entangled and if you try to seperate them, you'll possibly kill all 3.

:\ it's a bit of a pickle, since there's not much you can do about seperating those plants now.

My suggestion?
Get a pot that's about 4 or 5 times larger than the one you have.. and repot all 3 as one plant.

whatever you do, don't try to seperate those.. unless you want to kill them

p.s. i also suggest putting them into 12/12 now.