I started off with 2male 2 female.The first male disapeared then i found a dead female,then my large albino cory died and i saw the area around its anal fin was red then the 2nd female emperor was the same(dead with the red area) and i have just found my last male dead,and just yesterday i saw him with a red area in the smae place(alive though)
Any ideas what could have done this? The other cory and other fish are all ok.