Bru Vigor

Do you use bru vigor?  If so, when do you add, in the boil or the fermentor.  Same question applies to yeast starters.  Bru Vigor or no Bru Vigor and is it added to the boil?

Never heard of it. A Google search makes it seem like yeast nutrient and not many shops sell it. What does the package say?

Never heard of it. I add some fermK or FermO to my starters.

I don’t add anything to my starters. Never saw the need to do so.