Possible reason for suden death of royal gramma?

[m12345y]

Bought from recent LCK shipment last week, it had started eating pellets, but suddenly it's dead today. No visible wound.

[james72]

Caught using cyanide?

Bacteria bloom in tank?

White ich ?

[m12345y]

I tend to believe its cyanide but since no one else replied, I guess others who bought from the same batch are doing fine.

Also no ich, or else my tangs will get ich too. And no vowel bacteria bloom.

Thanks for your reply anyway. Let it be, I will try with another specimen see how