My fishes just suddenly died

[caelt]

This morning I woke up to fine 2 firefish and my prized wyoming white dead. They were very healthy and active yesterday and showed no signs of distress. to my horror this morning i found all their bodies lying at the same place. I have pictures of their dead bodies if anyone can tell me what the problem is. i checked salinity and temperature and there is shrimp goby and fireshrimp is active in my tank thanks for the help. today is a sad day. the pictures below are of the 2nd firefish that was struggling before he died shortly after. all their tails seemed to be a little nipped

 

[AZMSGT]

Electrical or Heater failure?

Readings on Ammonia? Nitrites? Size tank, how old is the tank?

 

[Daddy-o]

Chlorine/chloramine?

 

[LAReefer4Life]

Ammonia spike?