If them all seperate instances, you can make them move different speeds that looks cool.
Also, i have bad news.
I think you just need to check for resources with also checking current triangle enemies (EDIT: BUT IF YOU DO THIS, I HAVE NO IDEA HOW TO LOSE THIS GAME? RIGHT?
I mean you should use
if (triangle_resources - triangle_enemies > 0) sendTriangleAttacker();
if (triangle_resources > 0) sendTriangleAttacker();
AND another issue: Sometimes i can't see shape of attacking enemy because of health bars of planets, you can make them transparent, or can change their layer to behind of enemy layer.