On the advice of Sophie, I adjusted the shader settings on the resource

to be local to the scene so not all CRTs flashed when one got hit.

scenes/enemy_crt.tscn

@@ -27,6 +27,7 @@ void fragment() {
 "
 
 [sub_resource type="ShaderMaterial" id="ShaderMaterial_gas3w"]
+resource_local_to_scene = true
 shader = SubResource("Shader_emiuq")
 shader_parameter/toggle = 0.0
 
@@ -237,6 +238,7 @@ scale = Vector2(0.99999857, 0.99999857)
 shape = SubResource("RectangleShape2D_4gyqm")
 
 [node name="MoveTimer" type="Timer" parent="." unique_id=1928257014]
+wait_time = 0.75
 one_shot = true
 
 [node name="ShootTimer" type="Timer" parent="." unique_id=1985644907]