Recently bought. I've soaked some dried cannellini for 24 hours. I then cooked then in a soup recipe for a few hours.
Now why is it that some (not all) of the beans are still a bit tough. Most of the beans are soft, but every now and again I get a dud bean.

Is there a way to ensure even soaking \ cooking?

I heard adding a potato and a tomato to the cooking beans can improve this. Any thoughts?