Concern for my chalice.

[Don's tank]

My chalice was doing well, but then I noticed this white/ dead spot right in the middle of the area where it was growing. Does anyone have any ideas/suggestions?

 

[dbartkow]

is it covered in sand?

 

[Don's tank]

is it covered in sand?

The very bottom is in the sand but the rest of it is not and the section in question is towards the top and never has sand on it