How are they acting that makes you think they are unaffected?
That's a lot of Stars for that tank. What are they eating?
There are only a few hobbyists I know of that have been able to keep a Linkia Seastar for long. If the Stars are roaming actively all over the tank, it's because they are frantically seeking food but not finding it. It's their last burst of energy to move to where there is food. If they were in the wild they would have moved into new territory but in a little closed system, all they can do is move around in circles. Eventually they will slow down and never move again. Sorry.