I have been trying to get to support for some time now. I have questions about what to do with GND+ pins in EPM7128slc84-15 devices. What happens if the pins are left open.

Pins 7,19,32,42,47,59,72,82 are all hard GND in that package and must be grounded.

Not exactly sure what you mean by GND+, but if you are referring to UNUSED OUTPUTS DRIVING LOW you can leave those unconnected if so desired, or connect to test pads so you could possibly use those at some future time (in an ECO or test mode, for example).