star polyp base going yellow?????

[stumpy316uk]

i have notice that one of my star polyps has got a yellow base but there is new growth which is coraline algea colour.

any ideas
http://i945.photobucket.com/albums/ad296/stumpy316uk/DSC00937.jpg

[kingfisher62]

Yes , purple is the normal color for the matting. It could be algae discoloring the matting . Are the polyps acting normal?

[stumpy316uk]

they aren't opening fully

[romsoccer12]

looks like a sponge or algae is growing under them. try rubbing it with a toothbrush and see if the yellow goes away