Purple Stylophora dying??

Hi everyone,

I would be grateful if anyone could help me. My purple Stylophora has always been really healthy and has even been sprouting. However the last couple of days it has really gone down hill and I think it is dying.

It is my favourite coral so I would like to save it if I can. I have tested for Nitrite, Phosphates and Ammonium and all parameters are at 0. The only changes that I can think of that may have effected this coral are

1. I used some aptasia x in the tank but I was really careful. Could this be the cause?
2. I also bought a sexy shrimp about a week ago. Could he be the culprit?

Any advice would be gratefully received.

Thanks in advance.