coraline on button polyps

[rexxx]

i have a nice group of green button polyps under my pc lights and have gotten huge since i got them,but i have noticed some discoloring what looks to be coraline algae growing on the center of the green disks it pinkish and wondering if this is normal ,they are still opening and doesnt appear to bothering them (YET) i thought i heard that they had a mucous on them that didnt allow this to happen ,any thoughts?

 

[Shamrock317]

I had coraline grow on the stems but not on the tops, and they did fine. Actually, the colony has tripled in size since I noticed the CA growing on a few stems. Not that this had anyting to do with the sudden growth or anything. Just my thoughts