A few days ago the temp in my house dropped really low overnight and I didn't think a thing of it and I didn't have a heater turned on in my tank but my tank dropped maybe 5 degrees. My leather coral hasn't let it's polyps come out and it's lost some of its color for about a week now... Half of the coral had its polyps out a day or two after, but none that I have seen since then. What can I do? And how do I know when it's dead so I can take it out and not harm anything else?