Whenever any coral starts behaving differently, the first thing I reccomend is to check all 8 parameters to ensure they remain unchanged from our last results.
Torches should not be near anyone as they pack a power sting. It is sometimes hard to see some stingers as they can fully retract them, then, push it out multiple inches. Frogs and hammers can touch each other, but some distance is always reccomended.
All the "E" coral family, the torch, the frog, and the hammers HATE changes in Alk and this one parameter is the most important and can easily flux out of range as there is not much in water to start at the 140-180 ppm.
As you know, corals love stability in the eight major parameters. Any one or combination of will PO corals.
The only other thing might be something "bugged" it, a fish, another coral, a snail, a crab, but if so, it should reopen.
If not these, from a basic point of you, consider running activated carbon for a week. That could rule out chemical ware fare, or some unwanted toxin in the water, but this usually effects more than one.
IMO, these are the most common causes........hope that helps you a bit.....good luck.