Why do my beans stay rock hard?

I am cooking navy beans in a crock pot. I soaked them for several hours. I put the crock on high for two hours, then turned it off and let the beans soak for 24 hours. I drained the soak water and put in fresh water, added moles, brown sugar, mustard and onions. I cooked beans on low overnight and they are still rock hard and not very brown ... like they are refusing to soak up any liquid. HELP! I have heard that hard water can cause this, but I have an Artisan well and I don't think that is the problem...