My corals, including scolymia and cynarina, don't like the lower end of acceptable alkalinity (120 mg/L should be like 7 dKH according to
this conversion table ). I'm trying to keep 8.5- 10dKH, but this is personal reference. They also don't like the rapid changes, the dripping bottle, like Agu did, would be a good way for adding alkalinity supplement.
Also, I kept mine in direct sun (souther window, late autumn and winter) in the very shallow water, the high temperature wasn't liked too, tolerable - within 80.5F.
It did better in a separate brains tank, and in the tank with the few soft corals, than in mixed softies/LPS tank, but the last had tendency to produce a lot of detritus in a short time and have a low alkalinity (7-7.5 dKH), so it's hard to say, was it the influence of the soft corals or the tank conditions.
In a clean tank with a good light, even with spare feedings, it grow big quite fast.
Proximity of the heater (within 2"), with the flow from it right in direction of the coral - anothing thing that may contribute to the worsening condition. But mine contracted, not had a droopy mouth.
For an open mouth, my guess would be toxins, temperature, direct strong flow and low alkalinity - either of them.
All of the above was about the pale green kind of scolymia.
