Here's an update of what I've done based on vee's feedback, but now I'm getting the issue where one enemy ship seems to be firing and the others don't fire at all.
Occasionally I get the error where enemy ships have a fire rate that is insanely high, like 0.1 or something, which shouldn't be possible because the default fire rate is zero. Any ideas why this might be happening?
<img src="http://i.imgur.com/OmhMRfr.png" border="0">
SpaceGame.capx