1st, When the light is off at night, i.e when the polyps are not opened. see if you can spot any nudibranch crawling on them using torch light. if see those, remove them. It may be good if you can add a natural predator such as yellow wrasses to consume these pets.
2nd, is the zoas under direct current? if yes, probably change a location.
3rd, stretched - means the polyps seems to pull themselves upwards in order to get more light.