Need help with my girls tail!

[aemaki09]

So, I got this black dragon HMPK girl a few weeks ago, she had been spawned not long before I got her, so I didn't think much when I saw a chunk missing out of her tail, just figured that whoever she had been paired with but her. I QT'd her for a week and then added her to my sorority/community tank and she was doing well. I woke up 3 days ago and saw that half of her tail was gone! (Pics at end of post) she is still acting and swimming normally, so I don't think it is bothering her, but regaurdless I removed her from the sorority and put her into QT with AQ salt.
It looks absolutely horrible and isn't getting better! Can someone please help me get her fin to improve them quickly?


Housing
What size is your tank? 26 gallons, moved into 2.5 for QT
What temperature is your tank? 80*
Does your tank have a filter? Yes
Does your tank have an air stone or other type of aeration? No
Is your tank heated? Yes
What tank mates does your betta fish live with? 6 other bettas and 6 cories in main tank.

Food
What type of food do you feed your betta fish? NLS
How often do you feed your betta fish? 2x/day

Maintenance
How often do you perform a water change? 1x/week on main, every 2 days on QT
What percentage of the water do you change when you perform a water change? 30% on main, 60 on QT
What type of additives do you add to the water when you perform a water change? Tetra aqua safe. And AQ salt in the QT

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia: 0
Nitrite: 0
Nitrate: 10
pH: 7.6
Hardness: unknown
Alkalinity: unknown

Symptoms and Treatment
How has your betta fish's appearance changed? Missing half her tail, compared to only 1/4 a few days ago
How has your betta fish's behavior changed? Hasn't
When did you start noticing the symptoms? 3 days ago
Have you started treating your fish? If so, how? AQ salt, extra clean water
Does your fish have any history of being ill? Unknown
How old is your fish (approximately)? 6 months

[LittleBlueFishlets]

In the first pic, I see a chunk of tail missing.... In the 2nd pic though, what's the whitish stuff just above her tail? Is that on her (or part of her), or is it something in the background?

Could one of your other girls have been taking nips at her?

[aemaki09]

It's connected to her. That's what is making me the most worried. I would normally just let time, clean water, and 10 days of AQ salt help heal it, but with that fuzz ball thing there I am worried!

[LittleBlueFishlets]

I'd be freaking out too.... What meds do you have on hand? (I figure that if you list them now, it may help our resident experts in making some recommendations.)

[aemaki09]

Right now I have AQ salt, and Epsom Salts.
I had Jungle Lifeguard and Furan-2 but I ran out during my columnaris treatment around christmas.

I will go to the store and grab whatever is suggested tomorrow, or whenever I get a suggestion.


Also, I forgot to mention, when I first recieved the girl, this is what she looked like::



then last week she started developing red where her fin rays were, and where her tail is now missing. If that is helpful at all.

[blu the betta]

my jungle lifequard isnt working so i dont think its that reliable.

[aemaki09]

Yeah. I only used it until I got furan-2 on hand, and cant figure out what happened to the rest of my stash of it.


Edit:: I also added some crushed oak leaf into her QT just now, hopefully that will help a little