Salt licks are not needed with a good diet.
Please forget about most of the junk that is sold as "treats" and "supplements", many of them contain dairy, sugars/honey, colourants. Piggies also do not need vitamins in their water. All it does it turning the water green with algae in no time flat, but you can't control the intake and any vitamins go off in a very short time anyway.
Herbal treats are OK as an occasional treat and in small quantities.