setColorTransform flickering when applies on a typed group

Divergence

Hi!
I am trying to create something like Galaxian.
I have enemy spaceships that I store in var enemies:FlxTypedGroup<Enemy>;
When bullet overlaps an enemy I call

	public function onOverlap()
	{
		HP--;
		this.setColorTransform(1, 0.4 + (HP / 10), 0.4 + (HP / 10));
		if (HP <= 0)
		{
			kill();
		}
	}

this is what happens in the playstate loop:

override public function update(elapsed:Float)
	{
		super.update(elapsed);
		FlxG.overlap(enemies, playerBullets, onOverlap);
	}

	function onOverlap(enemy:Enemy, bullet:Bullet)
	{
		if (enemy.alive && enemy.exists && bullet.alive && bullet.exists)
		{
			enemy.onOverlap();
			if (enemy.alive == false)
			{
				explosion = new Explosion(enemy.x, enemy.y);
				add(explosion);
				explosion.Perform();
			}
			bullet.kill();
		}
	}

Seems I do everything right but after the first overlap all my enemy spaceships starts flickering and disappear...
And it looks like a complete chaos.
I have no idea how I can fix the issue... could anybody help to resolve?

Divergence

Solved.
As I am using typed group to store all my enemy ships I have to set Unique for loadGraphic in my Enemy class everytime I create a new instance.
Otherwise HF optimizes memory usage and store only one graphic object in vertex buffer and when I try to repaint one particular enemy it overloads the vertex buffer.
The following resolved the issue (one small 'true' at the end):

loadGraphic("assets/images/enemy.png", false, 24, 22, true);