If there are no swings, and your nutrients and other parameters are stable, I suspect your lighting is still too high. This is why a PAR meter is essential. I have a single Kessil AP9X over a 36" x 18" x 18" tank, it's rated for SPS Dominant tanks at 36" x 24" x 24" at 185 watts. XR30s are SPS Dominant at 24" x 24" x 30" at 210 watts. I bring this up because I am running mine, which states SPS dominant at a shallower depth than yours, at 25% and you're running yours at 60%. Those LPS are likely getting BLASTED with light. Euphyllia (Hammers, torches, frogspawn) are crazy adaptable to light, they can do just fine in 300 PAR and 100 PAR, but things like Acans, Scoly's, Candy Canes, Blasto's, etc, all prefer 50-150 PAR, and exceeding much beyond that takes an aggressive acclimation.
If I was you, I would try and rent a PAR meter and map your tank, you might be surprised at just how much light your sandbed is getting (even at 25% I am still getting 250 PAR on my sandbed at the outer corners and closer to 350 in the dead center...) You're in the Louis, so you should give SaltyUnderground a call and see if they rent PAR meters. I love that place.
