Fuzzy Tailed Roseline Sharks - Need Help Fast

I will try to make this short. About a week ago we purchased 2 Roseline Sharks for our 30g. The tank was fully cycled and ready to go, its only inhabitant was a parrot fish that was moved to our 55g. After 1 day their colored had started to really come back after the stress of the lfs and moving home with us. The next day their tails were covered with white "fluff." After doing some research I thought it was some sort of fungus, so we began treatment with quick cure. So far - no good. The are not getting better and have in fact gotten worse, neither fish has much tail left at all and they still have the fluff. I am including some pics in hopes that someone can point me in the right direction as to how to treat these guys. I have waited a long time for these 2 and I hate to see them suffer!
Today I have started treatment with Maracyn and I think I am going to revisit the lfs and get some Maracyn II for a little combo help.

Any advice would be greatly appreciated!

Thanks in advance!

1. Zeros across the board, temp 76, I do not test for ph, hardness etc.
2. Description listed above
3. about 50% a week water changes
4. The last few days I have added Quick Cure and Melafix, today only Maracyn
5. These 2 are the only guys in the tank
6. 30g
7. Removed a parrot fish and then added these guys last week

Yes it bacterial columnaris, yes get the maracyn two as well as that what you use maracyn one and two, good luck.

Wilder said:

Yes it bacterial columnaris, yes get the maracyn two as well as that what you use maracyn one and two, good luck.

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Well, this is a losing battle. One of the fish died yesterday and the other is on his way out.
I called the lfs and they said they have had problems with all of them. They also said that they have been treating the tank every which way they can and have made no progress on whatever this. A new strain of something ugly? I hope not.
I do know that I am about to lose a fully cycled tank!! Dangit
But the store is going to give me the full $60 credit on these 2, so I least I get something out of it.

Better luck next time I guess.

You can gets really bad strains of columnaris wiping a full tank of fish out, in cases like that you will need a strong antibiotic.