Is this fin rot? How to treat?

[meese-a-mew]

Is this fin rot? I can't get pics because its on my red irian rainbows. I just bought them yesterday and I think they have fin rot. It looks as if the fins tips are turning a bit white and melting but is only on the bottom back fins.
I have some JUNGLE FUNGUS ELIMINATOR and I just treated my tank but it looks as if its getting worse.
HELP!

 

[Delapool]

That sounds like fin rot to me or some sort of bacterial infection. I've never used the jungle fungus product so can't comment there. I understand water changes can help.