Did sharon turn to Brad after Nick started up with Phyllis or did Sharon chea first? Why did Nick and Sharon's marriage fail?

sharon cheated on nick several times before the whole phyllis and brad situation

nick cheated on sharon with her bf and sharon cheated on nick i think twice...all this happened way before the whole brad and phyllis stuff...sharon has a nack for cheating

what about the time nick caught sharon and victor kissing? so yes sharon was first!

what about nick cheating on sharon with grace?

what about the time when nick cheated with grace? which came first?