Female Guppy having babies, but still very pregnant days later?

Hi, I am experiencing strange behavior from one of my female guppies. I have never had this problem or situation before and I am completely stumped.

I have a female guppy who gave birth to a good amount of fry on June 3rd, but she never got any smaller and her gravid spot remained dark. A week later she had more babies, a lot more. Her gravid spot turned red (she is a very light yellow color) and she was a little smaller. But I noticed this morning that once again she is huge, her gravid spot is black and she looks like she is about to pop. (It hasn't even been a week since she gave birth again..)

All morning she has been hovering around the top of the tank not moving much. She is avoiding the others as well. She doesn't look like she is dying, just very inactive.

Anyone ever had this problem before and know what's going on with her?

Tank info:

20 Gallon
Occupants: 4 female guppies, 1 male guppy, 3 snails, 1 Corydora, a few ghost shrimp, and a bunch of fry.
Live Plants
Sand Substrate
Temp: 81 degrees F
Carbon filter

My ph levels are fine, my nitrate levels are a little high though and I'm going to do a 10% water change today. Done a 25% water change 2 days ago.

Note: All my other guppies seem to be doing fine. Another female gave birth just fine and slimmed up. No fin rot, no other kind of diseases and my fry are doing very well.

 

Are you sure that you are not overfeeding them. Sometimes black base appears their stomach due to overfeeding.
A picture could help.

 

I'm sure I'm not overfeeding. They get fed a small amount everyday, except the one or two days a week I let them fast.

All my other fish are doing well. No bloating or strange behavior.

As stated above, she just keeps popping out handfuls of babies..

So far I have 3 different sized fry in the tank. Her first batch, her second batch, and another handful from a different female. The first babies were born on the third. So she has given birth twice now within 13 days and remains boxed out.

-Would take a pic, but my camera needs charging and my 1 and half year old misplaced the charger.. And I don't have a smart phone. XP

 

You say your nitrates are a bit high; can you elaborate? What are the exact measures?

Funny that this thread popped up because one of my females did the exact same thing a few days ago. She gave birth, but stayed large, and three days later gave birth again.

I don't think it's anything to worry about. My female is now fine, belly has shrunk down again. The inactivity is probably due to the fact that your female's about to give birth again. Stress can also both cause labor to stop and bring it on prematurely, so that may be it. I think females can also carry multiple batches of fry at once, but I'm not sure.

Either way, just keep an eye on her. I think she'll be fine.

 

According to my strip my nitrate levels are:

NO3- Between the 40 and 80.. So between the safe and unsafe zones
NO2- About 2.0ppm

Everything else is perfect. I've been struggling the past few weeks to get my nitrate levels to go down, but it's slow going. My filter is for up to 40 gallons and once a week I do a 25% or more water change. I am going to start doing small water changes every other day until I can get those levels down. It's frustrating.

And I am sure I've caused some stress during the weekly cleanings and having to fix the live plants that decided to come loose.

I was wondering if she somehow held onto extra batches. I know they can hold sperm.

 

NO2 is nitrite, which is not good. It signals that your tank hasn't cycled fully. You're also having really high levels of nitrates there. Do a 50% change immediately to bring both of those down. Like you said, you'll probably have to do extra water changes to help with that.

She may be holding the fry because of water quality.