I never put medicine on a frog without knowing if it has something.
There is no such thing as preventive medication.
My vet told me, treating is acting on a disease you have diagnosed.
Without diagnosing what is wrong it is of no use to start medication.
Especially the heavier medication is something you must not use in season and out of season..

That is why you quarantaine newly aqcuired frogs.
You put them in a tank where you can easily obtain stool,
let it examin by a vet or someone experienced and act to that.
When something seems wrong and the stool is ok, you should swab to check for bacteria or fungi, but most of the times you will clearly see when a swab needs to be done.
If that's the case, better not buy the frog in the first place.

How do you think it would be when you get chemo therapy because you have a running nose.
First you see what is wrong, and you act to that.
How can you apply a medication to something you don't even know is there?

I will bet you, that 99% of the Chytrid "infections" isn't even examined by a trained person.
I'm sure that most of them aren't even treating Chytrid, simply because it was never there!
They are just applying athletes feet spray on a sensitive frogs skin,
no wonder it's acting weird.