I would love to see pics. It does sound very odd. It might be because of all that fertilizer. After the initial composting and fertilizing of the garden in spring, I don't feed my beans anything else, and they grow/produce very well.
Hopefully someone else who knows for sure chimes in.
Remy

Maybe someone can recommend an easy to use digital camera, or one with better software so I can reduce the size of the images. The camera I have takes images larger than my monitor screen.

Remy, is the Bosnian Pole supposed to be cutshort in a teardrop shape with a pronounced point? Do you have any in that shape? I thought they were supposed to be round.

The Bosnian Poles look like colorful Romano beans. So they are plump and sort of cutshort shaped. Hold on I'll find the pic...

So, a slight tendency to cutshort shape, probably exaggerated by use of foliar fertilizer. After nearly a month of drying, very few of the black on cream seeds are beginning to show a light tan where the brown will later appear.

Another bean with this late browning is the Snowcap or Porcelain. Fresh shelled Snowcaps are large beans, red flecks on cream, some with a dusting of fine red specks in the background where, after drying, a solid mustard brown will appear.

Have also noticed that the olive green Ma Williams will darken to brown in one year and red brown in two years.