Help Please Fish Dieing

[eel]

Can anyone help I have lost 2 Marble Hatchets within 2 days and I haven't a glue why. Tested the water and Ammonium and nitrite were both 0 and I always do a water change like clockwork every week.
They are in a small tank 60lts with not many fish in there 1 Bristle nose, 1 butterfly loach, 1 Ram and 2 Hatchets left. Looking at the fish and they all look in good health no diseases. Any Ideas Please

 

[fluttermoth]

Not a lot to go on there really...
Do some extra, larger water changes and make sure the hatchets are getting a really good diet, including some live or frozen food.

 

[This Old Spouse]

How did you test your water? Did you use an API liquid test kit or just strips? How old are your fish?

 

[Mr Melt]

EDIT - nevermind misread the question >_>