Is a letter from the drs. Office and rental lease enough proof that dependents live with me

It depends. Why do you need to prove this, and to what entity do you need to prove it?

My tax prep screwed up my papers and I received a letter in the mail about an audit and for me to send proof of residency for dependents

Yes, these documents can be used as proof that your dependents live with you.

Here is a list of other records that can be submitted to document that your dependents live with you.

• School records or statement.
• Landlord or property management statement.
• Health provider statement.
• Medical records.
• Child care provided records.
• Placement agency statement.
• Social service records or statement.
• Place of worship statement.
• Indian tribal official statement.
• Employer statement.