I Have Weird Looking Neons Should I Be Worried?

[dgerow3]

Ok i have 4 neons i noticed that two of my neon tetras look rather round and have what appear to look like bumps or a bump on the bottom of their belly and the other two are flat. Should i be concerned or is this normal could the rounder ones be females?? I never could figure out which ones were males or females.

 

[Truck]

have you just fed them? if so its normal