How can i increase enemies health over time?

I currently have a game where I spawn in 5 hoardes of enemies every 10 seconds. However, they do not get stronger as time goes on. How would I achieve this?

public const float maxHealth = 100;
public float currentHealth = maxHealth;

I was thinking I could just call the script from the spawner and multiply the maxHealth by a multiplier and be done with it. I can’t figure out a work around. Any help would be appreciated…

public double HPs = 200;

void Update () {

    HPs = HPs + 0.01;

is that the right answer ?