How do I avoid multiple substract life on the same event

I've made a pseudo space invaders "clone". My problem is the following :

if my ship gets hit at the same time by 2 invaders (when they are way down on the screen), my life counter will go from 3 directly to 1.

For now I only have one row of invaders using the same object.

I verify if my ship collides with enemy and then the actions are :

Destroy myShip

Destroy enemy

Substract 1 from life

Any help would be appreciate,

Ben

I would suggest tacking a Trigger Once While True event at the end