How do you know the cya is going down? Unless you are draining and refilling it shouldn't be...if it is you've got other problems.
Was your FC down at 4 ppm because the pool is using it up so fast? If it is, you need to redose your chlorine more often and shoot for a little higher level.
Was your FC down at 4 ppm because the pool is using it up so fast? If it is, you need to redose your chlorine more often and shoot for a little higher level.