that's a lot of yoga. I love yoga!! In 1 month, you haven't had much time to build up a lot of muscle, but by using your body as resistance, I wouldn't be too surprised if you had more muscle from yoga. It also helps you be in touch with your body, so maybe you're carrying yourself differently. When you're already smaller, just a few pounds can also make a difference with how you look. I bet it's a combination of all of them! Keep up the yoga, it will get even better