This was the one I used that I mentioned was very close to your recipe, just about half the size.
It's called aunt Clara's recipe.
That's what many people would think about leavening. Read this (around the muffins in the picture, a paragraph or two before you get to that picture).
I also think it's the leavening. It can create an ammonia-like smell if you're using too much and that may be the yeasty/rice aroma you're picking up.
That article is great for describing some of the basics of leavening. ^^
Also be sure that your product is fresh. Baking powder is good for up to a year, but baking soda is only good for 3 months.