Fish not eating and thinning

[DeepSeaDiving]

Hi so I just lost a guppy, don’t know why but he has had what looked like fin rot for a little over a week ago, so I treated with Melafix, but it still had a black tip on tail a week later. Then I noticed two days ago he looked incredibly thin, I only have three guppies and after I first put Melafix in all three fish stopped being that interested in food, they ate some of the good stuff like blood worms. The sick fish was thin and lethargic and wouldn’t eat so I moved him to a quarantine tank. He was dead yesterday morning. He was breathing heavy as well. The only other meds I have is paracide by blue planet for external parasites like flukes, but I thought it could be gill flukes so I put that in the quarantine, but it must have been too late. Now one of the other fish is looking thin so I treated the main tank with the paracide. But I’m worried cause he’s not that interested in food still and just pecks and spits out food even blood worms. I have included a photo of him and the other one for comparison. The last is the healthier one. Pls help, I have ordered general cure online cause Australia has nothing in regards to internal parasite meds. It’s from USA so won’t be here till may june. Could it be parasites? I can buy multicure by blue planet but that only covers ick, velvet and fungal stuff

 

[Autumnsky]

Guppies are a fish I like to deworm on a regular basis if getting them - as a standard of keeping. Before doing that, had a number of deaths before I realized it was likely internal parasites.

Can you get liquid goat dewormer with Fenbendozole from the livestock store? In USA, it is a brand called Safeguard.