Persistant bacterial infection....

First off I'd like to introduce myself.My name is Andrew and I have been
keeping goldfish and tropical fish for a little over a year now.I finally
got around to setting up my news reader and emmediately found groups
regarding fishkeeping among others interests.

Anyways...I have a female pearl scale who for the past few months has
been plagued by tiny bloody spots on her body.The spots seem to fade and
reappear at random.They don't seem to be affecting her other than the fact
that she is not growing as fast as my other goldfish.She eats well and isn't
lathargic.

I have tried every remedy I could find and nothing seems to
help...antibiotics,salt baths,melafix,etc.

My water conditions are good as far as pH,ammonia,nitrite and nitrate
are concerned.I don't imagine she can last indefinitely in this state....the
infection is bound to win out sooner or later.

Has anyone here had similar experiences?If so how did you fare in
finding a cure?

Any ideas/suggestions would be greatly appreciated.

Thankyou,
Andrew