Because they are Zoanthids. and they do as they please. They have only been in your tank a VERY short while. I have some that I have had for YEARS. Dinner plate sized colony. They cover at LEAST 1/3rd of my available rock surface space. sometimes they are closed up.
give it time and dont sweat it until they are closed up tight a balls for at least a week. then you need to see what may cause their issue.
give it time and dont sweat it until they are closed up tight a balls for at least a week. then you need to see what may cause their issue.