Labour Death?

[LyraGuppi]

My Orange Tuxedo Variatus Platy had been acting pregnant for a few weeks, then today she looked like she was going to pop. The other fish (Guppies, Platies) were bullying her, so I put her in a separate tank to give birth. All day long she would sit at the bottom and pant, her tail sticking way up into the air. When I checked up on her once I saw her mouth touching the floor, and her tail nearly straight up. She was jerking and gasping and her anal hole was enlarged and stretched, or so to speak. Later on I saw her literally spinning..she looked like she had lost control of her swimming entirely. She was breathing heavily and pushing, her anal hole still stretched. It looked like something had gotten stuck and later on she settled in an upside down position for about 10 minutes before dying.
What happened?

 

[fluttermoth]

How big was the separate tank you put her in? Did it have a cycled filter? What water did you use to fill it? How long was she in there before she died? Did you test the water and/or do a water change?

 

[LyraGuppi]

How big was the separate tank you put her in? Did it have a cycled filter? What water did you use to fill it? How long was she in there before she died? Did you test the water and/or do a water change?

Size: About the sie of a breeding box.
Filter: It didn't have a filter but it had an airstone. I would have put her into my 10 gal, but my tetras were in there due to a ich breakout in my 20 gal. (Fixed now)
Water: I use a mix of clean, treated tap (We have no chlorine in our water) and cycled warm water from the tetra tank.
Time: She was in the box for about 8 or 9 hours.
Changes: I did a few water changes to remove ammonia and the ph was around 7.5.