Resolve FPS drop with touchesMoved?

Question

In my SpriteKit game I have two sprites that rotate towards the point of touch. Also I have enemy sprites that fall from the top and travel down with increased frequency over time. After about thirty seconds of continuous touch with touchesMoved the sprite rotation and enemy sprite movement become very choppy as the frame rate drops to 30. I figure that this is caused by too much graphics processing on the main thread. Is there any way to handle the sprite rotation through CADisplayLink inside touchesBegan and touchesMoved?

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?){
    for touch: AnyObject in touches {
        location = touch.location(in: self)
        let DegreesToRadians = Pi / 180

        let rightDeltaX = location.x - rightSprite.position.x
        let rightDeltaY = location.y - rightSprite.position.y
        let rightAngle = atan2(rightDeltaY, rightDeltaX)

        let leftDeltaX = location.x - leftSprite.position.x
        let leftDeltaY = location.y - leftSprite.position.y
        let leftAngle = atan2(leftDeltaY, leftDeltaX)

        leftSprite.zRotation = leftAngle - 90 * DegreesToRadians

        rightSprite.zRotation = rightAngle - 90 * DegreesToRadians

        }
    }
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    for touch: AnyObject in touches {
        location = touch.location(in: self)
        let DegreesToRadians = Pi / 180

        let rightDeltaX = location.x - rightSprite.position.x
        let rightDeltaY = location.y - rightSprite.position.y
        let rightAngle = atan2(rightDeltaY, rightDeltaX)

        let leftDeltaX = location.x - leftSprite.position.x
        let leftDeltaY = location.y - leftSprite.position.y
        let leftAngle = atan2(leftDeltaY, leftDeltaX)

        leftSprite.zRotation = leftAngle - 90 * DegreesToRadians

        rightSprite.zRotation = rightAngle - 90 * DegreesToRadians

    }
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    for touch: AnyObject in touches {
        location = touch.location(in: self)

        leftSprite.zRotation = 0

        rightSprite.zRotation = 0

    }
}