Depending on how you are keeping the car, this may not be Tesla's fault. You have had the car for a year and only driven 20k miles. Most Tesla drivers plug their car in either every night or every other night. Telsas have a lithium ion battery. If you plug your car in every single night, that will wear down the battery, fast. It is why most people have problems with their phone batteries. They never let their phones get to zero and always plug it in overnight letting it just sit there and suck in power. That seriously damages the battery over the long term. The same principle applies to Tesla's lithium ion batteries.

The Texas heat could also potentially be exasperating this problem, depending on how you store it (since I'm guessing you don't have a climate controlled garage).