But it would seem like there would be some California required time period had passed since the last work was done, then they are just trying to scare someone into paying with unenforceable liens.
I do believe that there are many California specific mechnaics lien procedures and that any out of state advice, beyond working with the title company, could be very wrong.
Good luck, I hope it is cleared up very quickly!
When you closed on your transaction, did you get an owner's title insurance policy?
If so, contact the title agent about this, and any other liens from the developer's non payment, that may come forward
The title agnet will get that handled for you.
Best of luck