I had 6 white clouds, but lost one to this problem. Now I have 5 and 2 are affected. I'm not sure what it is, so I researched on the internet and I thought it could be a fungus or columnaris. I treated the tank with melafix and pimafix for 10 days. That didn't help so I isolated the two fish affected in a different tank and treated them for 5 days in "API fungus cure" which has the active ingredients of Victoria Green and Acriflavin. Today the treatment was over so I gradually put them back in the tank with the other fish. This treatment turned the two fish quite pale and you can see the abnormal growth more clearly in the pictures below. You can see the unaffected white clouds in the picture too. Do you think this might be lymphocycstis? I can also post my water readings if you like but everytime I test they always come out normal.