Deaths in tank

[tampa]

In my 55 gallon peacock/hap tank I have excellent water conditions (just tested). In the last week or so I have lost 2 fish (1 male and 1 female). All of the fish in this tank have "grown up" together since I set up the tank about 10 months ago. I was wondering what (who) might be killing these fish. The only fish that I have in there that I thought might be responsible would be the Malawi eye biter, HOWEVER, I not seen it being aggressive towards any of it's companions. Most of the fkish in the tank are in the 2 1/2" to 3" size range. Any thoughts would be appreciated. Thanks

 

[Sicklid]

What species died? What do you feed, and did they look 100% in the days leading up to their deaths, or were they looking pale w/ clamped fins, seeking refuge, etc.?