Cory Cat with possible fungus *pics*

[Iodizedfate]

Here are my parameters:
65 Gallon lightly planted freshwater.
Temp: 75F
Ammo:0
trIte:0
trAte:10
PH:8.0

I do 40% water changes once a week.
I use Prime for de-chlorinator, dose Excel every other day, dose Flourish Comp once a week after water changes and feed every other day (I think I might give a little too much food at times)

So one of my Cory Cats (green I think) has a growth on one of it's fins. It's white and sort of looks like a piece of rice. First thought was that it was ick, but looking at pictures online it looks too big and it's only on the one spot.

He is acting fine and it doesn't seem like it's hurting him. None of my other fish have it. I think it's fungus but I'm not sure. I've attached some pics to see if anyone can ID it for me.

What is it? What should I do to treat it?

 

[1 LARA]

You know if every time near water changes someone mostly black molly gets a white spot on here.

 

[Iodizedfate]

You know if every time near water changes someone mostly black molly gets a white spot on here.

Not really sure what you mean by this, but this is the first time I've seen this in my tank.

It's been up and running for 6ish months. I've had the Cory's for around 3 months I think.

Newest fish are 3 guppies and 2 dwarf gouramis and they've been in the tank for 2 or 3 weeks.