Missing Something?

[AlexandraDanielle21]

I added my first fish to my 40 gallon tank two weeks ago. I started out with 6 platies and 2 ballon-belly mollies. Last night, my fourth platy died and I am struggling to find a problem. My levels are as follows.
Ammonia-0
Nitrite-0
Nitrate-20ppm
Ph-7.5

The mollies and 2 remaining platies appear to have nothing wrong, but neither did the other ones who passed away. They didn't have any problems swimming, discoloration and they continued to eat. Any ideas on what could be wrong? Please help

 

[Zimmanski]

Possibly just bad stock or too much stress from being in the store and making the transfer to your tank, sometimes these things just happen and it sucks. If all your parameters are in check then really there's not much to say what exactly happened.

 

[shellieca]

+1 with Zimmanski. I would ask if you acclimated them properly? Also, was the water before or after the fish were added? You may want to try purchasing fish from a different store if you can.

 

[AlexandraDanielle21]

+1 with Zimmanski. I would ask if you acclimated them properly? Also, was the water before or after the fish were added? You may want to try purchasing fish from a different store if you can.

I made sure to introduce them to some of the tank water mixed with the water that I purchase them in. They swam in this before I moved them to the tank itself. I checked the levels the day after I put them in, and even then the levels were not that bad. I want to say its bad stock too, but I still feel bad that they passed away.