communication between 7 bluetooth modules
The HC 05 modules will only pair with one device at a time.  You might be able to come up with a scheme where a module configured as a master acts as a hub communicating with 6 modules configured as slaves.  The master would pair with each one in turn, transfer data, and pair with the next.  

It seems like a lot of effort though, are you sure you can't use Zigbee, ANT or another wireless method that already includes mesh networking features?