Zoas shedding outer layer of skin

[Rupture Reefer]

Previously my zoanthus were not doing so good, so I moved them to the sand bed. The past two days, they have been shedding their outer layer of skin, and have turned a little purplish brown. (Pic below). What does this mean?

 

[Reefbuds]

Idk man ive never heard of any coral shedding skin.