Sick Fish, [Shubukin] being bitten by other

Hi

Thanks for all the help... BUT the fish died last night, it was really
ill, it was a fighter but couldnt take anymore , the ulcer was very
deep, was white around the edges dont know if that meant it was
healing or not.

I have two more fish with symptoms, (already lost 3) one comet small
infection on the back near the fin, one Gold fish about 3 small white
marks.

These two look healthier, but dont want them to go down the same
route... how will i know if the mlachite worked and the pond is clear?

How long does it take for ulcers to heal, these are not open ulcers as
yet

Also yes my dad did add tap safe stuff to the water he always does.

Once again thanks for the help.

Waseem