The past 8 months have been hell for my tank as well.. a mysterious die off of my sps.  Not even RTN, just a fast colour loss and then eventual death.  Luckily all my caps have recovered, almost to pre-die off stage.  I had a huge algae problem I finaly got under control with my Rabbitfish..  god I love him 

 ....  now I have the small valonia.. which I grabbed some Emerald crabs for..  I tried them out in a small tank with a huge chunk of valonia and they went crazy for it, so I hope they work 

 ...  Otherwise, things are finally starting to get back to normal.
With going to school full time and work, its been tough to keep the tank maintenance, I basicly set a timer for 1 hr and just power through water changes etc..
 
Good luck