Prodibio makes a host of products. I'm assuming your using the Spots & Velvet Salt water product.
I would not use this product to treat any diseases. First, they do not tell you what is in it. Second, it's long expired, almost 3 years now.
The other consideration is that the only effective treatments for SW ich are hyposalinity or copper usually in the form of cupramine. These treatments must be done in a quarantine tank, no exceptions. If you do not have a quarantine tank, you need to get one.
See this post which will point you to other threads on the subject.