Finsky: IMHO, it is unlikely that it was caused by reef additives.
I got impression that chili is more sensitive to what is excreted by microalgae, diodogorgia gorgonian, red cyano, decaying aiptasia or just react on high content of the organics in the water (if skimmer doesn't clean water well after feedings). Looks to me like it requires more clean water, than the rest on non-photosynthetic corals.
All my 4 kinds of chili coral - vertical cactus-, fingers-, miniature fingers- and large tree-shaped - opened at full the same day after bringing them home from the store. Most of them stopped to show polyps weeks later, stayed closed for several months, then opened again. Later that repeated, but it wasn't season related.
Temperate chili corals (Alcyonum sp., that look like the tropical chili corals we are keeping) have a dormancy period, which appearance is quite similar to what I saw with my chilis. Except that for temperate waters chilis it was season related, and all mine were bought in stores, who import exclusively from tropical and subtropical areas.
The last sound idea to try that was given to me - and I continue to use it now - to keep them in turbulent flow. Only moderately strong, not as strong as for dendronephthya and scleronephthya. Rather as for diodogorgia gorgonian.
It could be reflected from the glass, rotating around in the cube shaped tank, or in corner, where unidirectional flow that already started to lose its strength bounces from wall and creates mini twister. Wavemaker is even better.
200gph and 150 gph within few inches were too strong for mine, no matter was it turbulent or not.
Previous good idea - keeping chili in refugium type of the tank didn't help.
And one more thing: in first days I could see the open polyps only in the morning, before the lights were on. As soon as lights were on, the coral retracted polyps within minutes. Later, in dark tank (low ambient light, as in north facing room) chilis were open almost all day long.
Other reefers had different experiences - see this thread and chili thread at Ultimate Reef Azoo forum for details - and I still don't know, was it because they were different species with different requirements, or advanced type of skimmer kept water clean, or they didn't have diodogorgia, nuisance microalgae and cyanobacteria, aiptasia or isopods, bothering this coral.