Ok I think that should be easy to fix, just checking first. Are the shadows are supposed to remain on the ground and fade opacity out when the enemy is jumping, and you don't want the upper row enemies to have shadows?
If that's the case I wouldn't recommend using the "is overlapping" condition to achieve what you are doing
-Use a container like you have
-Make an event to position shadows: Every Tick, set shadow.X to enemy.X. Set shadow.Y to floor-height
-Make an event to control removing shadows for higher enemies: If enemy.y => maximum-height set shadow.opacity to 0
-Make an event to control shadow opacity for jumping enemies: If enemy.y < maximum-height set shadow.opacity to 100-distance(enemy.x,enemy.y,shadow.x,shadow.y)
I'll do a quick example to show you what I mean