What is the problem with my ember tetra
I recently noticed this particular male ember tetra starting to lose some of its colors, and its belly is also a bit sunken even though it's eating and being very active. My suspicion is that it has contracted callamanus worms, as I had problems with callamanus worms in another guppy tank I have, and I believe it somehow got into this aquarium. I didn't see any red worms coming out of it (typical of an advanced stage of callamanus worms), but I believe it's possibly because it's in the initial stage of a possible worm infestation. I couldn't see its poop to analyze if it's healthy or transparent, so I'm not sure. I'll post some pictures of it in comparison with the other ember tetras that are healthy and haven't shown signs of disease yet. In any case, I applied a dose of 3mg/L of Ripercol (active ingredient levadamisole) to paralyze and expel any possible worms from the fish. Unfortunately, I had to use it on the entire aquarium even though I have ramshorn snails, which could probably kill some of them since I was told levamisole affects invertebrates. Anyway, I came here to seek guidance or tips from someone who has gone through something similar.
Note that the parameters are 82-84 degrees Fahrenheit / 28-29 degrees Celsius. Regarding the pH, this is probably a point of concern. I've been using DIY CO2 with sugar and yeast, and I don't remove the diffuser overnight. I believe this causes a pH fluctuation. I don't know if this possible fluctuation could have affected the fish or lowered its immunity, but with my tests i saw that the fluctuation isn't huge, about 6.8 ph during the day and 7-7.2 at night