Help coral

[moosehead]

this i woke up to coral that has lost tissue on some of its branches overnight.dont know why this has happenned. Didn't change anything or do anything drastic cleaned my overflow box yesterday.Put selcon into the fish food as i do every week .Any help would be greatly appreciated.
PH around 8.14
KH 8.5
CA 415
No3 is 15-20

 

[moosehead]

Is there a easy way to edit this to the sps coral section were I should have posted it oroginal

 

[chimmike]

No3 is kinda high. Temp? Salinity?

 

[moosehead]

Temp is 77.5-78
Sal 1.0245

 

[Giants13]

what kind of fish do u have ?

 

[Taahirs]

Nitrate seems to be the cause of it rtn

 

[moosehead]

I have a yellow tang,pink spotted goby,mandarin goby,2 clowns,blue tang,and a royal gramma,I feed twice a day my sis shrimp and n.pellet food.I may need to feed only once a day?