Frogspawn base receding

[blmurphy1982]

Best way to describe it - everything else seems fine but the calcium carbonate base of the coral is slowly disappearing. Alk around 9 calcium around 450 and mag around 1300. Any ideas?

[ReefAddict]

Any pictures?  Is it the base right underneath the flesh or further down?  I have had some where the base is under the sand and eroded, but it has never affected the coral and it has continued to grow.