Unhappy hammer coral

[Yasha Hase]

Noticed my hammer coral wasn't very open and has this white stringy thing on it's base any ideas on what it is?

 

[Irishman]

Have you checked all of your parameters?

 

[Irishman]

Have you checked all of your parameters?

 

[Yasha Hase]

Ya I just took all the tests I have
PH 8.3
Calcium 410
Ammonia 0
Nitrite 0
Nitrate 5-10
Alk 8.5
Phos .005 ppm
Salinity 1.026

I did just do my weekly 25% water change yesterday