SPS Dying Possibly due to Biopellets?

[Thesaltwater]

This is exactly what I was going to say. I don't know why they still make non-recirculating reactors.
You need to control the effluent. In this case you could simply turn a knob down to a drip.
Also that could be a lot of light. I just got a PAR meter and found I had 515 PAR on middle sandbed with an 8bulb ATI 6" off surface/24" H tank. PAR in middle was 7-800 burning some corals. Go conservative and move fixture to 9-10 inches if not already. Lower with older bulbs.

Oh crap LOL, never thought about that. my fixture in about 4 inches off my tank, definitely moving it up!