You could drain off the brine and add fresh water in its place or just rinse it off a bit before you use it. You will probably lose some of the good guys, but better than throwing it away no?
Last time I made kraut, I think I under-salted. It seemed to be fermenting along just fine, but when it came time to put it in jars, the brine was very slimy. I would pick up a fork full and there would be a long string of brine instead of drips. Quite unappetizing. I think the problem was too little salt let a yeast outcompete the lactic acid bacteria. I gave it to my chickens and they wouldn't eat it either. So, to the compost it went.