I read through a lot of this, but maybe I missed the part where you described how the corals were dying. Are they bleaching? All slimy? Or are they retracted until death?
IME, I just purchased a new t5 tek fixture to upgrade from my CF
and 1 t5 ho
that I had, and light was causing a huge problem. I went from very low, with super old bulbs, to 4 (out of 6) brand new bulbs. Even with reduced photo period I still managed to bleach my birdsnest and chalices, gorgornians, ect...
Frog Spawn was fine though...
This is a good read: Feature Article: Effects Of Narrow Bandwidth Light Sources On Coral Host And Zooxanthellae Pigments — Advanced Aquarist | Aquarist Magazine and Blog
About the effects of narrow-band wavelength light (specifically related to LEDs) on corals, and photosynthesis.
My best guess to the root of your problem is still the light, I've read people with new Raidons sometimes start at 20% efficiency in their ramp up cycle.