Gigantea HELP

[Greg 45]

Picked up a health gigantea from a fellow reefer . It was diong good for 4 weeks. Recently lost apatite to eat. Tryed more flow less flow. There are three 400 watt reflux 12 k bulbs over tank. Mouth starting to stay open during the day. At night shrivels up to a small size.
ANY HELP WELCOME
sorry no pictures