Medications should be use when necessary and some of us has learn through out years to make an educated guess, As one can never be certain until a pathogen has being positively identified by microscope.
However many of us do deworm and treat for parasites like fluke.
This is a quick view to my quarantine method is kind an a guide as I don't do always the same but is more or less. You can read others on the quarantine section.
When you received a new fish , just give them clean water , feed them the next morning, and do daily WCs, after of few days to a week depend how they arrived and how fast they acclimatized .
the second week but the first one of treatment I personally treat with metro first.(preferable in the food like FDBW if they are eating well as they should)
three days rest
third week I treat with praziquantel preferable prazi pro because dilute better.
three days rest
fourth week I treat with Flubendazole or levamisol.(in the food preferable for Flubendazole)
Now observation for a whole week with clean water daily WCs . I don't treat for antibiotics if not necessary.
At the end of my quarantine I give the fish a light pink PP bath for three hours. I usually do it for the fish they are going to join with to. (so everyone start in a clean).
So yes you should keep medications the difference is to use it as prophylactic measure or disease treatment.
Again when the fish are eating I put the med in their food instead of the water that is for metro and Flubendazole.