You can use this:
h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
text-transform: none !important;
}
but it also depends on the font family you use. By default, JA Brickstore uses "Unica One",cursive font family so it looks like uppercase already.