Janam Kundli is forbidden in Sikhi, even though it is followed by some people.
Those that do follow Janam Kundli often say something such as "It can't hurt, and maybe it will help" or "I'm not hurting anyone by doing this"Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/sikh-sikhi-sikhism/3219-horoscopes-janam-kundli.html
But our Gurus taught us to have faith only in God. Not in star charts, not in fancy stones that have one power or another, not in anything other than HIM. If a Sikh follows such things thinking desiring to see some kind of positive change in her or his life, then isn't that leaving faith to something other than Waheguru ji?