Sick pygmy cory?

Bender81

Large Fish
Feb 17, 2005
131
0
0
43
Toronto
#1
One of my cories look swollen, he's sorta has a bulge on his under side. His eyes are sticking out too, I can see them when I look from the top view. Colour is also a little lighter than the others now, but other than that he's acting normal. This change in appearance is definately new and he's the only one of the 4 that looks this way. Any idea what could be wrong with him?