Have you checked the Min Size? Below the Size? If you have it on 100%, just reduce it, you can see the difference. Just reduce it to 50% or something. Both the Size and Min Size play important roles on the size of the brushes. Hope this help! ^^V
I was wondering that your colouring style wasn't that complex. I'd rather say that you can use it very well and that you know how to play with the light and shadows. No wonder you can make so many amazing pictures! Keep improving!