That's what I thought at first but the tanks they die in all have perfect water.. Ph 7, ammonia and nitrite 0 and nitrates at about 10, temp sits at 27 degrees. They usually die at about 2 months and at that point they eat twice a day , crushed flakes, shrimp pellets and baby live shrimp which is always available in their tanks. I think it's just poor genes to be honest