i went through the same thing....i thought mine would be different....but there is no getting around it.
bearded dragons want their own space. without it they are competing for the same resources and it can get ugly.
If its not missing limbs or bites, its health problems... Your large tank may be big enough to bisect for two habitats but i dont think three will be favorable. Also as they grow older even seeing other dragons through their glass is unhealthy and stressful for them.
So you have time while they are young to figure out the change, but as they grow older they will get more aggressive and pick on each other. they can only be housed together as a temporary condition (as in pet stores).