infection?

I think my angelfish has septicemia. For a very long time- years actually- she's had redness where the pectorals meet the body. I came up with septicemia before but thought that couldn't be it, as all the accounts I read said that fish die very quickly from the disease. This week, in spite of the fact that I've been feeding more lightly, doing larger water changes and cleaning the filter sponges more frequently than I used to, she's got redness on the body margins, and fin rot on all. Her dorsal is split, anal fin shortened, pelvic and tail fin edges ragged. I feel like I'm failing her.

I started reading more, and somehow my searches turned up a different set of case studies this time- several with fishes that lived years with septicemia. Damn, the symptoms match. I bought kanaplex and started treatment on sunday- today was the second dose. I don't see any improvement yet, although the fin deterioration might have slowed down, it's hard to tell. She still has appetite, but hides in the back nearly all day and doesn't come out to greet me as often, or as eagerly.