Treating Finrot During Crayfish Molt

We bought a 40 gl tank to accommodate our rescued inhabitants, because the 20 gl we had was obviously too small.
After moving the lucky bait (minnows and crayfish) into their new home, some of the minnows showed signs of finrot which we immediately treated with API Melafix and API Pimafix. They've been treated for 3 days and today would be the 4th (improvement showing).
BUT...this morning I did a 20% weekly water change and lo and behold, one of the crays molted over night.
So here is the question: Is it safe to continue the finrot treatment for the fish?
Is the finrot coming back with a vengeance if I stop treatment for a couple days?
Would the stress this treatment causes to the crayfish make him so exhausted that he'd drop dead? (He is tired, sits in his cave with part of his old skeleton and is trying to heal because he lost an arm in the process)
Once I add this stuff, the scent drives them nuts and they do a marathon around the glass for hours which he is too exhausted for and has no balance with only 1 claw.

So, to do or not to do is the big question.
Safe to skip a day or 2 of finrot on the fish?

 

I would quit the use of Melafix and Pimafix. They're useless. Water changes would go much farther to help the fins heal than those. You can definitely continue water changes after the molt.

 

I found something that worked within 24 hours and made the 'fungus' literally fall off the fishes eyeballs, healed fins almost completely and made them all eat again.
Got a few more days to go on the medication but it seems to have worked like a charm. It was also safe for the crayfish.
And YES, I did stop Pimafix and Melafix, they did not work, in fact 1 fish went septic and I put it out of its misery.
To think that Melafix is nothing but an antiseptic, what a scam API is.

 

Nice! What medication is it?

 

Something called Artemiss by Microbe-Lift.
I had researched for hours on finrot and stumbled upon Dr Foster&Smith. Now someone else than told me that site is actually owned by PetCo. So I drove there and they had it hidden on a bottom shelf behind a metal stand of flyers.
Now I also know what caused my fish to get this in the first place.
I bought them from the store, they got netted, I netted them again into a 20 gl tank ( at the beginning), Ammonia spiked because I added more than my filter could handle and the Ammonia started eating away the flesh, causing finrot, reddish skin ( which I thought looked pretty on red rosy minnows, am I an Idiot!), and odd behavior like bouncing against substrate and bucking like a horse. They were injured from multiple nettings and then swam in their own urine for days, Prime does not get rid of the burning sensation.
Ammonia and Ammonium really needs to be at absolute 0 for finrot to heal.

 

Prime should prevent ammonia burns and the burning sensation, as it binds to it to protect your fish. Glad it's working though!