Are all 5 in the same cage?
If Volt and Luna were fighting, I'd pull them from the group. Leave the others that weren't fighting together and watch them super close.
Get a temp cage for each Volt and Luna, separate them for a week, and see about reintroducing them. I'd start with reintroducing Volt, since it seemed that Luna started the fight. If everything goes well there, try reintroducing Luna. If all goes will they are together but watch super close.
If it doesn't go well after reintroducing Volt, pull Volt again and try introducing Luna. If it still doesn't go well, you have to decided...leave Volt and Luna by themselves in their own cages, or separate the remaining of the group to find them a friend.
Just my opinion. =)