My Red Belly Pacu's need HELP!!!!?

I have 2 red belly pacus, 2 catfish and 2 sucker fish in a 40 gallon tank. My 2 reb bellies look like they have "bubbles" all over there bodies. The other fish seem to be fine (I can't see anything wrong with them). They were fine yesterday, but today my boys noticed the "bubbles". The tank has been up for almost 2 months and I have not did a water change this week but plan to do so once I found out what I need to do to "fix" them. Can I save them? And how?