Argh! First fish death in a year and a half!

[humdedum]

...not counting fry deaths.
pH steady at 8.4, water medium hard. Daily 20% water changes because of relatively new tank, plus I have fry. Temp is 78 F.

Okay, so I bought 3 platys (one male, two round females) ten days ago. There was a persistent 0.25 of ammonia until I knocked it out May 9.

Female One, Honeysuckle, gave birth unexpectedly (without boxing) on May 6 and so now I've got three fry captured.

May 11 - Female Two, Spinway stops being a chasing bully and starts being chased and bullied. She hides away in the corner and behind heaters. I assume this is because she is now ready to give birth, and now the other female suspects something. Heavy breathing.

Fast forward to May 12, and suddenly Spinway is no longer round. Note: she was never boxed up or anything. Just round. I assume she has given birth overnight. Unlike the other female, though, she doesn't automatically resume tank life as normal.

Now it's Friday the 13th (oh darn), 9 am, and she's still hiding away and still breathing heavily. Won't eat food that drifts in front of her nose. I assume birth was harder for her than the first female and figure she'll bounce back soon.

Do some stuff, come back downstairs at noon and can't find her. Eventually see she's dead. Her tail fin is slightly nipped (by the other female, when she was still alive), but otherwise her body is unaffected by anything. No fuzzy growths, holes, missing scales, red scales, brown gills....

What killed her?

Ammonia, nitrite, nitrates are all good (as in, zero). Chlorine (zero), pH (8.4), and hardness (medium) has not changed at all. Nothing is off in water parameters.

So my town could have changed chemicals. My de-chlorinator "removes chlorine, chloramines, ammonia, and heavy metals". Nope, seems good.

Maybe the whole tank is affected. The other two adults are breathing normally, eating normally, swimming and acting normally. It can't be a toxin, because it's not affecting them as far as I can see. And then I have those tiny, sensitive fry. If water quality was compromised, they'd be the first to go, right? Nope, the little buggers are thriving like crazy.

I'm stumped now. I truly am. Stumped and irked, really, because I haven't had to net out a dead fish in a year and a half. I was even going to get a little whiteboard that said "No fish deaths for _____ days". Was she already sick, since she's relatively new?

Thanks in advance for reading this chunk of text. I just wanted to make sure everything's been covered already.

EDIT: Whoooooa, hold on here. I found some pure fish poo in my tank. It's not the other fish; I've had the wonderful opportunity to see them pass normal brown stuff. Does this mean parasites? Should I treat the other fish, just in case, too? The *ahem* isn't brown, or reddish-brown like when I feed shrimp, or greenish-brown like when there's greens, but white. Pure, unadulterated white. Sigh. Complications.

[emc7]

Since these are relatively new fish, you should be alert for disease signs. But a sudden death of a female in the days following giving birth is very common.

[humdedum]

I am keeping a close eye on both of the fish. I check them every couple of hours and examine each one closely for a couple of minutes. So far they're still healthy-looking though.

She was not very large, about an inch or maybe a little bigger, so perhaps it was her first pregnancy? I actually kind of hope that's the case (post-drop death), because otherwise it means some sort of pathogen is loose in the tank ready to kill the others.

[egoreise]

Awww no! I had something similar happen! I had a pregnant female that was hanging out at the top of the tank, tilted with her face upward. And then she had some pure white poo. I thought she was aborting.
Then I had an ich outbreak, she had it the worst. I think she was susceptible because she was so stressed out. I lost her while I was medicating the tank.

I'm sorry... I really hope it was just one of those natural things that sometimes happen, like what emc7 suggested, with the post-pregnancy problems.

[humdedum]

People Who Lose Pregnant Females to Sudden Death, Unite!

Yeah, that kind of sounds like what she was doing. I do wonder if she truly dropped them now, or just aborted that brood and things went wrong during the process...

I need Sherlock at my home, right now.

[PhsychoFish]

Jason killed her O.o
Friday the 13th IS a curse..

[Betta man]

I lost my female platy while in childbirth or um... fishbirth.

[emc7]

frybirth?.

[MetalHead]

white poo? interstinal parasites. TOS & Loha would be able to id it better but if memory serves epsom salt dips would help. I remember loha helping Obsidian with her pleco which had the same symptoms.