Hi there,
The general belief on this matter is that beardies are solitary and territorial creatures and so should always be housed alone.
So really the behaviour you are describing was highly likely to start sooner or later.
Males + females especially shouldnt be housed together because they can overbreed.
When beardies are housed together one usually becomes dominant causing the other beardie to not grow properly due to stress, which sounds exactly like what has happened in your case.
Beardies can and do attack eachother, unfortunatly dragons are not like dogs, who can be taught about naughty aggressive behaviour.
Dragons will think nothing of nipping off a chunk or tail/toe in order to defend their basking spot.
I rescued a dragon from a viv with multiple beardies in. She was small for her age and was missing a bit of her tail, most of her right arm, most of her right foot and alot of her toes.
Dont beat yourself up about not knowing, most ignorant pet store workers will insist that having two beardies is fine, but please do the responsible thing and seperate them perminantly.
Your dragons will lead much happier healthier lives apart.
Until you can get a new tank for your female Id suggest separating your viv with a section of cardboard immediately.
Holly