Best way to calculate sum of custom object holding numbers and returning sum as that object instance

Ok, so ive created an type Damage, that has a few values and is implementing IEnumerable + has some additional getters, like that:

 public class Damage : IEnumerable<float> {
     public float v1 = 1;
     public float v2 = 2;
     public float v3 = 3;
 
     [...]
 }

Instances of that class are assigned to game objects. Then i have controller, that calculates sum of Damages for every game object. There is problem, because i suppose i need high performence solution here, because ill be calling that sum in every iteration. I have thought of 2 ways doing that:

 public class Controller : MonoBehaviour {
     [...]
     
     public Damage GetSum1() {
         float v1 = 0;
         float v2 = 0;
         float v3 = 0;
         foreach (Damage damage in gameObjectList) {
             v1 += damage.v1;
             v2 += damage.v2;
             v3 += damage.v3;
         }
         return new Damage (v1, v2, v3);
     }
 
     private Damage damageSum = new Damage();
     public Damage GetSum2() {
         damageSum.v1 = 0;
         damageSum.v2 = 0;
         damageSum.v3 = 0;
         foreach (Damage damage in gameObjectList) {
             damageSum.v1 += damage.v1;
             damageSum.v2 += damage.v2;
             damageSum.v3 += damage.v3;
         }
         return damageSum;
     }
 }

And now lets analyze those solutions: GetSum1 - im afraid of allocating memory in every single Update iteration. That one can lead to enormouse memory usage. Its bad. Advantage is that i can make my Damage class immutable, which is more secure than mutable version. GetSum2 - with this solution i have to make Damage class mutable, which is less defensive, but it has much better performance, since i dont need to allocate new object in every single iteration.

I thought also about another solution - making Damage structure instead of class and than use first way. Why i thought about it ? Because i dont know how struct works. I know that structs are called "value types", so i thought they may be kind of like primitive types. Am I wrong ? Calling new Damage(v1, v2, v3) would be as optimal as creating just 3 floats inside a loop ?