I think the catfish are a big factor. They are certainly heavily competing with your bass for limited resources. Start to track the relative weights of your bass. Any bass under 90-100 remove and all catfish caught remove. Once most of the bass caught are in the 100+ relative weight range you can cut back on culling them. At that point I would consider adding forage. It sounds like you may have some suitable habitat for GSH. Get the catfish and bass thinned out and give them a try. Don't get carried away with removing all the American pondweed, it's excellent habitat for GSH.