Lately, my cakes aren't rising. I've replaced my baking powder and baking soda to no avail. Box (mixes) rise fine; it's just been my cakes from scratch. They are still tasting great, and don't feel super dense, but they're flat. Really flat.
I find scratch cakes do not rise as high as box mixes....if the taste and texture is fine, I'd say you are just not filling the pans high enough. It takes more of most scratch batter to make the same cake as it does box batter.
it may be the type of flour. for my scratch cakes, i've learned that if i use regular all purpose flour, they will not rise as much. i've started using self-rising flour and adding my baking soda/powder as usual. they turn out nice and fluffy. HTH!