Prefabs & Instances

I have a bunch of prefabbed characters that all have a "unitAI" C# script attached to them. One public variable in this ai script is a public enum list, which contains "player," "neutral," or "enemy" strings, and another public variable for me to choose which Owner the unit belongs to. Currently, whenever I make any change to the unit's other variables and apply it to the prefab, it'll change this Owner enum value to this particular instance.

So, if I've already placed a dozen of this unit in an area as Neutrals, and now I'm planting a bunch of enemies and change any value on my prefab, ALL of these prefab instances now become Enemy instances. I understand that this is how prefabs are built to work, but is there a way to flag or tag my enum variables so that changing the prefab won't affect this one variable per instance?