Sick and dying Glofish

[Mishi]

I have a ten gallon tank with fake plants and a bubble stone (in a volcano) that had 4 glofish and two young black bar endler guppies.



My starfire red glofish died a few days ago, I have no idea why. It was acting lethargic, hiding behind the fake rock formation for a day and when I got home it was dead.
Then a few days later my electric green glofish was hiding in the same spot, acting lethargic except this one had what appeared to me as some sort of internal injury... You can see it from both sides of its body, and underneath too...



and when I came home from work it was dead...
This is the second time I have seen this on my electric green glofish (had one a few months ago, same story)
And I think the only reason why I didn't noticed anything on the red glofish was because of the fish's color...
I have no idea what would cause this or what this even is...

Can anyone help me so I can stop killing these fish? I have gone through like 10 of these fish in the last 7 months...

 

[CoryFan]

The red gills and inflammation internally COULD be ammonia poisoning.
Would you be able to test your water for ammonia, nitrites, and nitrates for us? Posting that will help figure this out.
Liquid tests are more accurate.

 

[Mishi]

Yes of course.
Ammonia is .25
Nitrate is 20
Nitrite is 0
GH is 75
KH is 120
pH is 7.2

I use Jungle brand test strips, which I have heard aren't entirely accurate, but I haven't been able to afford the liquid test kit yet...