A month on and 2 out of 3 of the new goldfish have died, and all the remaining goldfish are infected with Crustacean parasite, Lernaea (Anchor Worms) - which can only have come from the infected fish, and could only have been the fish from Pets at Home establishment.
I am furious that having trusted a large scale brand my entire tank is now at risk. I will never buy pets from there again. We only went there because the fish guy at Brindley Garden Center was restocking and we were that side of town (usually we go to Fish World at the Reynolds Center)
I've sent this e-mail to Pets @ Home, I'll update if I get a response, but I'd check the health of your tank if you've brought Fish from them recently.
Don't worry, we are treating them now, and they do look a little bit happier, and as ever I'll keep you updated.