You may need to duplicate and modify a bit more. You can't use just one "flag" variable to control two different LEDs independently.
For now perhaps add a parameter to flipflop() to tell it WHICH of the switches it's reacting to and then flip a flag1 or flag2 and go from there?
But really if you're going to extend it to 6 LEDs each reacting to their own switch you should also start looking at using arrays for both. That will make the code much neater if you have something like (not real code, you'll need to look that up yourself):
for i from 1 to 6
if button[i] is pressed
switch LED[i] on
next i
Steve