Infection in Shubunkin

Hello

I have a big tail shubunkin with what I belive is an infection. It
started with the fish being overfed with puffed wheat - it then one
evening looked dead and lay like a banana on the bottom. But the next
morning it seemed completely recovered and fine again. Then over a
period of some days the shape of the fish deteriorated. The fins
rotted, it lay still in a corner on the bottom most of the time. Also
after some days the fins on the belly started getting red and the
belly of the fish got an odd bulging shape. Other fish started eating
off of its fins.
So I took out the other two fish and all the plants and made the tank
into a hospital tank. The tank is 70 litres with filter, heater and
one overhead lighttube. I started feeding the fish with Sera Bacto
tabs (pieces) only. I also gradually added non iodized salt to the
concentration 0,3 % like recommended somewhere on the 'net. I change
20 litres of the water every day as recommended on the Sera Bacto tabs
box. I also use (and have always used) recommended amounts of Tetra
AquaSafe. I keep the temp at approx 78 degrees fahrenheit. After
feeding Sera BactoTabs now for 5 days the fish has gotten a bit better
I think - it moves around more and has good appetite, but the fins are
still very red. Should I continue feeding BactoTabs or should I end
the cure after 7 days as recommended? Should I do something else? Any
help appreciated.
Thank you!

A picture of the fish is he
http://www.geocities.com/uggabotha/fish.JPG

oleas

Keep doing water changes and monitor the ammonia, nitrite, nitrate and PH
levels.
If you could post them that would help.

Shubs are pond fish by the way and need lots of room to grow.