Really like your design and colors! It reminds me of stained glass windows, which I love.
I think what may be causing you to second guess yourself may have to do with color placement of your golden yellow. It is in either top or bottom position in about half of your rectangles. But since they are not symmetrically arranged/ evenly dispersed this creates movement but it is not fluid movement if you understand what I'm trying to say. So try rearranging the rectangles several different ways and see if that makes a difference in how you feel about it. Maybe start by swapping column 3 and column 4?
Your sashing and cornerstones work great with your "windows".