Read the FAQ's at the top of this forum, particularly on hyposalinity and quarantine. You'll do better not to use bottled cures as most don't work. Don't do any more dips. They won't help and are just stressing the fish more. Can you possibly post a picture of what you're seeing, particularly on the tang? You mentioned the tang was sick before and you treated it? What did you treat with? Post all of your water parameters; nitrate, temp, salinity, pH. Do you have a quarantine tank? If not, begin setting one up now per the instructions outlined in the FAQ's.