First snippets from web are usually wrong.. be careful
to do pin change each pin goes to its own vector and each has to enabled in its group.
also you reaqlly should not try to serial printin interrupt routine it means you have system interrupts within your ISR and timing gets screwed
Set a boolean in ISR and check it in Loop and serial print if its set meaning you have been been in ISR.
I'm just going out send me a message with more details will outline some code for you..