Actually, in CA any sex with a minor under 18 is a crime. It's a misdemeanor if there is less than three years between them; a felony if more.
However, it is also true that unless you live in a very law-abiding town and the DA and police have very little to do, they are less likely to take up the cause of consentual sex with an almost-legal adult with someone only two years older than they, than they would if it were one of the younger girls.