I have a feeling your Corys didn't make it because they starved. Those fish are aces at locating food sources. My bet is that the small size of the tank and overpopulation and being unfiltered and underaerated may have caused the death of your Corys.
I'd just like to say this, the tank IS filtered and heated. I did put all four females into the tank once agian, only to have the larger female constantly chasing the new commers endlessly. Every time she even sees another, she goes after it until she loses it.
It always starts off the same, the larger girl flaring, showing her fins. After a few minutes, she chases all the other girls and cause them to become stressed.
Im also fully aware of the constant shift in container size from the females, and I'm also aware of what stress can do to them, which i dont want.
The tank is spacious and has a lot of room for all three girls. After moving the decorations last night, the larger one seemed confused at the arrangement, but, noticed that all the decorations remained the same.
My guess is that she knew that it was HER territory, and, even though the decorations were moved into different parts, she still saw it as her own. And she was the last one placed into the tank, too.
Another note: The CAE isn't going to be there long. If anything, its being pushed around by ALL my female betta's. I do intend to put it into the 75 gallon tank, but, its too small now. It WILL be devoured faster than it can zoom away by the much larger fish in the tank.