Apart from the white tubercules, I've noticed that some of my cheni have paler areas around the base of the dorsal and caudal fins, and a white edge to the dorsal fin. I'm not sure if these signs are all connected, or just something I've not noticed in a few of my fish before. Some don't show any of these signs.
No other fish have show any signs of illness at all until I spotted the white cloud today, which is breathing fast, struggling to swim and has a large bulge on one side of it's body. It's sat in the bottom of a breeder net at ther moment, and doesn't look like it's going to make it

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i'm about to do water tests- I'll post the results as soon as I'm done.
I've got no idea what this could be, or even if the cheni and white cloud are suffering from the same thing. Any advice would be much appreciated.