Take the parking spot away?

[Sean M.]

Purchased a fourplex close to Downtown LA a few months ago and now am trying to renew leases with my tenants and also start charging them for the second parking spot they have been using by parking tandem in the back. 

Facts:

- Tenants have been here for a few years now and all leases are month to month.

- Leases are on a one pager piece of paper and do not mention anything about the parking.

- Estoppel I got from last owner mentions that each tenant is using two parking spots. (Could this be a deal breaker??)

Also Do you guys know how I can renew my leases so I have a more secured and detailed Lease agreement with them?

Appreciate any input on this since I am a newbie and even my property manager says he has never took back any parking spot before !!!

Regards;

Sean