Reason for Hammer Coral melting

[Arnab]

I purchased my first hammer last week and it melted in 2 days in my tank. Tank is 2 months old . My alkalinity is low (around 6.5 dkh) but my LFS said that its a hardy coral and should not be a problem. Today I calibrated my Hanna Salinity checker and found my salinity to be 1.022 (earlier it was reading 1.026) . Can salinity be the reason for the disaster ?

Any thoughts ? I don't want to repeat my mistake.

 

[Anubisxii]

Tank is young, what are your other levels? pH ammonia nitrates etc

 

[Anubisxii]

Is there anything else in the tank fish or other corals?

 

[Arnab]

Tank is young, what are your other levels? pH ammonia nitrates etc

PH - 8.4
AMMONIA - 0 ppm
NITRATES - 5 ppm
NITRITE - 0 ppm
PHOSPHATE - 0.1

CALCIUM - 400
MAGNESIUM - 1360

Yes , There are 7 fishes (SixLine Wrasse, Yellow Wrasse, Bangai Cardinal, Tuxedo Damzel, Azure Damzel , 2 Clown Fish) and 2 more corals (Zoa, Recordia)