Yes, unfortunately they appear to be aiptasia & you'll want to kill them off before they multiply.
You can use lemon juice and inject it directly into the mouth or the stalk and they should die quickly..more info on this method here: http://saltaquarium.about.com/cs/msubpestaiptasia/a/aa061903.htm
There are many ways to do it but if you only have 3 and are fairly new to reefing (meaning you don't have an assortment yet of the bizarre chemicals that we all seem to end up with), lemon juice is a nice simple method.
Yeah Jim they are bad, make sure if you can't remove the rock from your tank to paste it with kalk that you turn off all the flow in the tank to keep it from blowing around.