The pin change interrupt is attached to a port which means that any pin on that port, so long as it has been enabled, will trigger the interrupt, PCINT0 is attached to PORTB which includes pins 8:13. PCINT1 is attached to PORTC (14:19 or A0 thru A5 if you prefer) and PCINT2 with PORTD (0:7).
You have your buttons spec'd on 7 and 8 which is one from PORTD and one from PORTB respectively. That means having to deal with different ISRs, which is fine and may be the way you wish to handle it.