I don't care much about the coral. It is just what you say, it is not doing anything for me. I moved it before and it got a little better. I will brake off the branch it is attached to and move it someware else for an experiment.Two degree swing between night and day shouldn't be an issue at all.
I doubt anything in your salt mix is deficient for it... it's a Kenya tree after all. Unless your SpG is way off through an inaccurate measuring device, I doubt there's any issue with your salt mix.
Where is it placed in the tank? Is it getting enough light? Is it being shaded?
It just seems weird to me that its not doing anything for you. Normally, the problem is that they grow and self-propogate like mad.