Why Do They Die

[Marky_Mark]

i have 2 clown kuli loaches and 2 kuli loaches and i came home today to see them dead, i checked the water and all is well, i do regular water changes,and the tank is at 28 degrees, there is no fish in there to bully them so why did they die?

 

[catxx]

how long has the tank been set up?
what are the other tankmates?
how big is the tank?
any new fish additions lately?
how old were these fish?
any signs of disease on the dead fish?