Guppies wont breed?

I was wondering why my guppies would never breed in my tank.


Timeline:
November 16, 2019 : Tank was setup and planted
November 30, 2019: 5 guppies were added three males two females
November 27, 2019-December 10, 2019: 3 males died.
December 11, 2019: A female ( bought pregnant) gave birth to 6 fries
December 19, 2019: The other female died
January, 6, 2019: Female was expected to give birth around this time and she did not. I started to notice beginning now that she was starting to get very skinny
January 11, 2020: added two females and two males
January 19, 2020: One of the females gave birth.
January 28, 2020: The "original" guppy die
And here I am almost one month later and neither guppies has given birth yet.

Tank info:
10 Gallons
Sponge filter and cascade 300

Water parameters:
Always stayed at:
0- 0.25 ppm ammonia
0 nitrite
0- 10 nitrate
All of the test were done before water changes

 

Do you have any of the 6 fry born in December or any of the fry from January?

Guppies get hardier the more generations you keep in your tank. The first generation almost always has problems when not bought from a reputable breeder. I would be concerned about internal parasites if one of your fish had a sunken belly. If you have any fry that are growing out, I would keep them and stop buying adults. Let them grow out and have their own fry. If they're dying too, something is really wrong.

I would also keep an eye on that ammonia and make sure it stays at 0.

 

Could it be because the male was infertile

 

Could you post a picture of your guppies? As mentioned above, it could be down to internal parasites. That’s being said, I have had trouble getting my albino koi guppies to breed.

 

My take on this is you should figure out why you're losing fish. If you solve that problem it will probably affect breeding success as well.