I have recently set up my tank, about a fortnight ago, and I bought four neon tetras to begin with. One recently died unexpectedly overnight and I’m not sure how. Everything was continuing fine and I decided to add the guppies, but recently after I spotted that all of the three neons appear to have bulges at the bottom. I have researched but can’t find anything generally specific to the change in my guppies. They generally seem to be sticking together and I can’t notice anything unusual other than the bulges. I will attach some images, help is greatly appreciated as I’m rather worried.