Hello tarek2 It wouldn't be exactly that
I would like, for example, that when a bomb explodes near enemies, the bomb's damage decreases the enemies' health. But when I do this, it only decreases the health of one enemy.
There is not much info, so will be impossible to help:
You say that you have a circle which you are using as the radius area damage, and when it hits multiple enemies it should subtract from their damage. That should work with any of the options they already provided you.
Enemy on collision sprites: ------> Sprite Subtract health
or
Enemy on overlaps sprites: ------> Sprite Subtract health
Any of the two should pick all the sprites touching the enemy.
Not sure where is the issue?
The example I provide you already shows you that is working with "On Collisions" which picks all the sprites that collide with the enemy.
You just have to replace the "destroy" action with sprite subtract Health.
But when I do this, it only decreases the health of one enemy.
If you are asking why isn't working your example then is impossible for anyone to know as they can't see your project. You gonna have to provide an example showing what is not working, so someone can give you an accurate answer. At the moment we just guessing.
It sounds like you have a Picking problem but we cannot move farther as we need to see an example to investigate.