Did the store sell them as a pair? I find most stores only carry males for obvious color and size reasons. Female appisto's tend to be very yellow all over. These two to my eye look like two males, one just larger than the other. But wait and see how they grow. Here is a good example of a male and female. The difference is pretty dramatic.
http://en.wikipedia.org/wiki/File:Apistogramma_Cacatuoides_Male_and_Female.jpg
Here is a photo of my male and female, different species but as you can see the female is very yellow.
http://en.wikipedia.org/wiki/File:Apistogramma_Cacatuoides_Male_and_Female.jpg
Here is a photo of my male and female, different species but as you can see the female is very yellow.
