Chalice turning pale

[ved25]

This chalice is losing color in this one spot hard to see in blue light but noticeable in white light any ideas the PAR is 100 or less in this spot not sure what I should do

Parameters are
Salinity 35ppt
Alk 8
Calcium 440
Mag 1350
Phosphate .07
Nitrate 5-10

 

[ved25]

 

[ved25]