It depends how long they have lived there. If any of them have been there less than a year, your 30-day notice was good. I assume you sent it certified mail, otherwise you have to reserve it in one the ways stated in Code of Civil Procedure section 1162.
If they have all been there for more than a year, you have to give them a 60-day notice. The notice must state a termination date.
If you have to bring an unlawful detainer action after the notice expires, you can tack on another two weeks to a month.