Sounds to me like you need stop dosing other stuff, and do a bunch of consistent water changes, which will get your calcium up, and help stabilize your tank.
It seems the problems with your candy cane are general saltwater tank stability/maintenance issues rather than a specific coral related issue. Parameters that far out of whack with Calc low and other high don't happen on their own with consistent water changes.
Get back to the basic, which will allow you to analyze what is actually happening, and then compensate accordingly. Until you know what's really happening with the tank, anything else you do, dose, add, subtract, will only mask what is really happening.