Unless it is obvious that this tenant caused it (eg previous occupant had no kids and this one does and you find a toy caused the blockage), I would pay for the first one.

CA has geographic and government blockages that make housing development difficult. 

When the plumbers came out to clear the drain, they recovered wipes from the toilet drain, which was causing the blockage to the main drain.

In cases where there is backflow into the house, it likely indicates a problem with the line from your house to the street (such as cracks or blockages).

For example, my lease states "Tenant shall be charged for repair of drain blockages or stoppages, unless caused by defective plumbing parts or tree roots invading sewer lines."

The lines could be big enough but have blockage.

Type of construction (wood frame or block?). Age

There's a chance the blockage occurs between a certain part of the sidewalk and the street.

In the case of a drain line, if there is a blockage at the point where the line becomes Common, it could be (based on your Docs) shared expense with a neighbor (such as in the case of neighboring, back to back tubs or sinks); or it may well be the HOA's responsibility.

Instead, you could just have a simple clause in the lease like mine: “Tenant shall be charged for repair of drain blockages or stoppages, unless caused by defective plumbing parts or tree roots invading sewer lines.”Then it’s pretty clear what you will and won’t pay for, and you don’t have to worry about trying to figure out what they shoved down the toilet that actually caused the clog (e.g. tampons, child’s toy, etc) because they’re responsible regardless.