I have my first tank and added 5 Zebra Danios to start my cycle. They have been in for 3 weeks and recently I noticed that one of them has gotten much larger than the others and has a different shape to it's belly. I was hoping someone could tell me if this was a pregnant female, a physical difference between males and females or a sign of some type of illness/parasite etc. Here are two pics: The first just shows the distended belly area, the second is with another Danio that has a different shape, all 4 of my others are the slimmer versions, only the one has the "budda belly" Thank you!

