Only one effect is removed per casting
Greater restoration is intended to remove only one condition per casting
You imbue a creature you touch with positive energy to undo a debilitating effect.
The description makes it clear that only one effect is removed at a time. So you would need a separate casting for each effect.
You can reduce the target's Exhaustion level by one, or end one of the following effects on the target.
You can't even remove multiple levels of exhaustion with one casting. The spell is simply intended to work one at a time.
None of the specifics of the individual spells implies that they override this
Feeblemind
The spell can also be ended by Greater Restoration, heal or wish.
Geas
A Remove Curse, Greater Restoration, or wish spell also ends it.
Modify Memory
A Remove Curse or Greater Restoration spell cast on the target restores the creature's true memory.
All these mean is that the spells can be removed by greater restoration, not that they are automatically removed when it is cast on the afflicted creature for any reason.