What if you turn off all the reactor, dose manually. Massive water change (80 to 90%). Shrink the photo period to 3 to 4 hours. Suck up all the sand, replace it or leave it BB.
Maybe I am dead wrong. But, I was facing the same thing with the old tank. Losing corals, after I transfer all the SPS to the new set up. They are actually showing signs of recovery.
The old live rocks should support enough bacteria that a cycle should be short. As long as the water temperature is not off too much, ick outbreak might not happen. Maybe its time for broken arrow.