I should coment on the ich treatment, which I missed previously. Characins are very sensitive to chemicals and medications, which is why many treatments usually recommend half strength with these fish. Malachite green is not good to use with characins, but having said that, I suspect (hope) the level of this drug in this product may be minimal anyway.
For future treatment, and ich is very common with new fish, if the fish species can tolerate it, raising the temperature to 86F without any drugs will usually work. Keep the temp at 86F for a full week, then turn down the heater and let the tank return to normal temp. If the fish cannot manage with the higher temperature, raise the tank temp as high as you can and use CopperSafe. This is not a strong drug so it is less likely to cause difficulties for sensitive fish [and I have had no losses using this with wild-caught characins like pencilfish and various tetra, farlowella, and even corys which are notorious for having problems with medications]. A good water change first, raising the temp some, add the CS, maintain the heat for one week, then return it to normal, and wait another 3-5 days for the next water change.
Here in North America, where kkomadina lives, we are seeing more issues with commercially-raised fish than used to be the case. For some 20 years I never quarantined, and I never had issues beyond ich which was never a problem (never lost fish to this) if caught right away. But over the past 3 or so years, both from my experience mentioned previously and from what I have read on this forum and elsewhere, this has changed noticeably. After my loss of half my existing fish in a display tank, I am now quarantining new fish for 5-6 weeks. It is a wise precaution these days.