Different things influence when a pullet starts laying. Being in California this time of the year the length of days will no be a problem for you. So at least you don't have to worry about that.
Breed can have something to do with it, but also what age did the pullet's mother and grandmothers start laying. You can get quite a difference even in the same breeds.
If I have 10 pullets of what I'd call a normal production full-sized fowl breed like Sussex, Australorp, Rhode Island Red, Delaware, Rock, or Wyandotte this time of the year, I'd expect one or two of them to start laying by 20 weeks. I'd expect half of them to be laying by 24 to 25 weeks, and probably all of them to be laying by 28 to 29 weeks.
I've had some start as early as 16 weeks. Just a couple, that's fairly unusual. I've had some not start laying until 9 months. Again fairly unusual. You have 6. Not a large sample size but not bad. As they are now 4 weeks old I'd expect you to see an egg or two in July with August being a good month.
Good luck!