So usb is in use, also when running Bluetooth.
Many different hc-05 outthere, mine needed extra power to function at all. My usb to ttl could not supply enough.
Some Bluetooth devices need a lot of power, so feed it with 5v (3.3v ) from separate power supply.
USB 5v might not be enough.
Feed 3.3 from nano might not be enough.
Is it possible to give USB hub separate 5v in?