I’d just quarantine for 2 months. See if anything starts to pop up and then decide to treat. Usually keep prazi and levamisole since i cont to buy wild caught fish. What fish are you planning to keep?
Same here.
Different meds are effective against certain pathogens, but not others, and many meds are in actuality, simply toxic substances in small doses,
so I see random treatment as something that could be counter productive over time, and wear on the the new fishes immune system..
As an example malachite is a somewhat toxic metal salt (even considered a carcinogen to humans), and might be effective against some protozoa, but may be a waste of time against an internal nematode condition.
Of course because where I live, I always end up with wild caught fish these days, a few parasites are almost guaranteed,
so observation in a controlled environment is needed.
But with some parasites, and/or viruses meds are completely useless.

The adults of the parasitic Lernaea above, are almost impervious to all legal or allowable over the counter meds these days, so physical removal was my only recourse.
Although its Larva were eliminated simply by using an elevated (and non-toxic) salinity.