1st year completed. Tenant's leaving a month early.

[Lue Brooks]

So I've completed my first year of being a landlord. It had its ups and downs but I have loved it. I will post about it another time if anybody is interested. I have one problem though. My tenants want to leave 1 month early. They gave me their security deposits and the lease says "it is to be refunded upon vacating, returning the keys to the landlord and termination of this contract according to other terms herein agreed." I've looked up and down this lease 3 times and have not seen anything about leaving early. (I know I have no excuse to why I didn't have that taken care of, but It was my very first month of being a landlord, and a lesson for me to learn from.) I want to know what you all think? Will I have to give the money back or is it automatically assumed that if you leave early the money is to be kept from the landlord? They had 2 kids and a dog as well. The kids more than likely messed something up so some of the deposit will have to be kept. I am also in the state of Texas.