looks like you have a pretty good pond already. I think you are right to get more bluegill in there. don't be afraid to move up your cut on what to take out to a pound or even a pound and a half. focus on taking out males if you can. It appears that your fish need more to eat. maybe they are eating all of the bass hatch and there aren't enough bluegill. get some cover in there for them too so the hatch can survive a little longer and provide bigger meals. if you catch any more big catfish get those out of there. they are competing with your bass for food when they get large. throw some floating catfish food and see how many cats you have. there might be several of those. my 2 cents. Good luck! Don't hesitate to take out bass, they need to come out probably at the very least 15 or even 20 lbs per acre every year.