Black Spot on chalice

[David tan]

Did anyone ever experiences black spot on chalice ??

A black spot suddenly appeared on my chalice and spreading.

something i notice algae on top of the black spot

Been in my tank for 3 months.

Parameter :
Sal : 1.025
KH : 8.5
Ca : 430
Mg : 1290
NI : 25ppm
point of sale : 0.03

 

[blaxsun]

Are these two of the same coral? (just trying to reference the spot in the second image)

 

[David Tanady]

Are these two of the same coral? (just trying to reference the spot in the second image)

different corals, i attache new photo with a highlight of the black spot .

it used to covered with flesh, but now its disappearing.