Thanks Wilder. No signs in the other fish whatsoever now, I think the treatment has worked - I know that sounds odd considering what happened to Dolly, but I suspect she was ill long before she came here and the stress of being split from her boyfriend stopped her recovering as well as the others - she really was very stressy. Blade looks better than when he first arrived, a million times better - no signs at all on him and his fins are looking impressive. The platy that began to show signs (a silver mark just in front of the dorsal) is completely better.
I think it's today that we can redose the tank. Haven't decided whether to do another dose of the meds or whether to add salt at 1% instead, but either way I'm hoping we're over the worst now and back on track. The first job is another big water change. I *must* get a new hose, doing it by the bucket is a chore and a half!