star polyps

[Snappy]

I have a couple of nice patches of bright green grassy looking star polyps that for the past 2 weeks will not come out at all. There is only the pinkish bumpy leathery looking base left. Parameters all seem to be normal and the other stuff in my tank is doing fine. It started the day after I put a large tiger cucumber in the tank but since it doesn't eat them I thought it to be a coincidence, yet that is the only change made in that time frame.
Anyone have any suggestions?
Thanks,
Greg