Is there something I can give my bunch that would help the cats that need help, but do nothing for the ones that don't need any help?
Nothing comes to mind. :( It sounds like some need more/less bone than others, but I'm not sure how you would work that in since you feed ground. :-\ Unless you give, say, a chicken wingette to those who have the soft stools.
I can't remember . . . were you also using the Vet's Best? Or, as the brain slowly engages, you were using it but stopped because it was causing problems?
The only thing I can think of, but I really don't like to suggest is, is add a little psyllium powder to the food of the ones that have soft stools. The problem with that is they also need a LOT of moisture with the food, because psyllium absorbs water, and you don't need their stool going to the other extreme.