What size tank and tankmates?
I've had dozens. Best to crowd them or start with a few and end up with 1 male and 1 or more females. Males, if not crowded, will kill each other and females that are rejected can get harassed as well. Since you only have four, watch carefully and remove any harassed ones immediately or they will be dead soon. (you've seen that).
They appreciate rocks that they can dig out around. So, I go with irregularly shaped rocks spaced around the tank. They'll dig out under them. No need for shells, I find they prefer rocks. Don't stack up the rocks, as that's not what they prefer and will only go there if chased there.
Very cool fish. I've kept almost 30 tanganyikans and if I could only keep one, this would be it. Fantastic personalily. They will breed like crazy once they get going. Dozens will turn into hundreds. They accept their fry, and fry of other adults. You can end up with dozens from multiple generations in one tank.
I'll link some video's as that's easier than trying to explain all the behaviors.
This is when I had four dozen in a six foot tank. You can see the rock layout I described.
telmats
Some others.
adults with fry
male breaking up a female squabble