Blue chromis always die on me

[Dans75G]

Hello everyone and Happy New Year. I need some advice about understanding why my blue chromis fish are the only ones dying. My 75g is over 4 months old with plenty of live rock and water tests that are almost perfect. I never neglect my aquarium. I'm always performing maintenance. For some reason out of all my fish, the chromis are the only ones dying and I always catch my crabs eating the carcass.
I don't have many fish, but the ones I do have look happy.
I have at the moment 2 clownfish, 2 dartfish, 5 blue chromis, 1 sand sifter, 1 6line wrasse, and 1 cardinal. I have these for about a month and a half.
The chromis are about 2 weeks
I used to have 11 blue chromis.
I feed at least 2-3x per day.

Can any one help me understand why?

 

[gafights]

I know they need to eat more often than most fish but unless your water is off that is about all I can think of. I have never had them so this is just what I have heard from friends of mine.

 

[begginersluck]

Thats very strange. Must be missing something here. I know some damsels kill each other for hirearchy but never heard of blue chromis doing it.