SPS tissue loss?

[OCDreefer]

So I have a few corals that have lost some tissue or bleached out near the base of the coral, but no more. It have been this way for some time on two of them. Everything else is great i'm guess it is do to lack of light? Any input would be welcomed. (and sorry for the bad photos)

 

[kevinpo]

Light can be one of several causes. Water flow (or lack of enough) can also be a cause.

Regards,
Kevin