Sinularia issue, base cracked,

[-XENOMORPH-]

So I had a 4 or 5 finger staulk 8 inch to 9 " long happy sinularia? Green. For a year. About 3 weeks ago, it started retracting. I had moved it away from an anemonee that was bothering it. I figured it would be fine. But now i notice a "tear"? In base and black stuff? And it has been shrunken up for a while. 2 weeks. Pics attached. Is it dying? Rot? Sick? Should I glue it closed? Infected? Remove it? Thankyou for advice.

 

[vetteguy53081]

So I had a 4 or 5 finger staulk 8 inch to 9 " long happy sinularia? Green. For a year. About 3 weeks ago, it started retracting. I had moved it away from an anemonee that was bothering it. I figured it would be fine. But now i notice a "tear"? In base and black stuff? And it has been shrunken up for a while. 2 weeks. Pics attached. Is it dying? Rot? Sick? Should I glue it closed? Infected? Remove it? Thankyou for advice.

May be lack of calcium requirements and even light