so far keeping corydoras I've lost 5 and have 3 left. I've been trying various things to keep them alive but they just keep dieing. I can keep gouramis, otos, and apistogrammas just fine, but not corydoras. I don't want to get more cories because I think they'll just die too. these 3 seem ok, but I'm worried 3 is too small a group. should I just give up on cories and rehome these?