Treating Velvet?

[Aquattro]

Honestly, I've done more harm putting them in a new treatment tank. The queen and wrasse are moments away from dead, the naso probably won't see morning. A clown is looking bad. The leopard wrasse seems fine, as do the 2 chromis and the mandarin. Yellow tang seems normal, hippo tang is dusted up pretty bad, but still swimming.

I just need to know the dosage using tabs, but at this point, I'm going to guess and just add 20mg/l of the tabs. I can't do any more harm than I've done already