Normal
Hi I honestly believe heat mats are a no no for tarantulas. All tarantulas will be fine at normal room temperature if you are comfortable they will be. I have about 10 brachys and all are fine at room temperature. As for it not eating don't worry I had one go over a year without eating. As long as you have got water available for your t it will be fine. A large abdomen is a good sign it's OK could be in heavy pre molt. Send a picture of your tarantula and enclosure