I have nursed my two LTA'S back to good health they both dropped their zooxanthellae.
First you need MH for lights
Second you need to feed it everyday if it doesn't take it don't worry it will eat when it wants, but needs to be offered meat I use whitebait, if you don't it will eat it's own flesh.
Third I have been adding reefbooster to the tank I'm sure this has helped
Forth I give mine some cyclopeze a couple of times a week
Fifth don't over carbon the tank
Six keep you water KH Mag etc higher end of scale
Seventh don't be in a hurry its taken one and a half years to bring mine back.
Wasp thought I would lose them.
Good luck