White cloud with persistant Columnaris

Hi all and my thanks beforehand for any assistance here. About a month
a go I noticed a very small,cottony looking patch on one of my white
clouds. I immediately quarantined him and after googling columnaris
gave the following medications:

Maroxy & Maracyn (together) - 1 round on the Maroxy and 2 rounds on the
Maracyn

Waited a few days with very clean water - he still had the cottony
patch.

Fungus Clear - 2 rounds of which the second was completed last week.

The patch is still there. From the front it appears smaller but from
the side I can see it still sticks out from his body. I'd say the patch
is the size of a stickpin edge, if that.

What am I doing wrong? I have never had an outbreak of columnaris in my
tank so this is new to me. I was confused with some of the information
I found on the illness, some sites seemed to recommend treating it as a
"true fungus" hence the Maroxy. Many said use antibiotics, hence the
Maracyn. I have used Maracyn several times in the past for various
illnesses and always had good luck, so I hoped it would do the trick.

I feel so bad for this poor guy, he's all alone in this bare tank. I
want him to get better and go back to his home tank. I also don't want
to keep medicating him if the patch is not getting better!

My thanks to all for any help!!!