If the bass are getting thin, you likely have a forage issue. 90% of lakes we survey the owner thinks they have "lots" of forage (bluegill/redear/shinners/shad/minnows). And in virtually all cases they do not have enough. The amount of food a bass eats is astonishing. Removing 100 small bass (1/2 to 1 lb) from a 10 acre pond is likely 1/4 to 1/3 of what you need to remove. Try getting more aggressive with your harvest and see if the weights come up. Moreover, try a measure and weigh a few fish and compare to a relative weight chart. Again, my experience is that most landowners think their fish are "healthy" (meaning their weight is where it should be. But most over estimate their weight by 5% to 15%. Anything over 95% is good. Anything below 85% is poor. 85% to 95% your doing OK.
If your not familar with how to use a relative weight chart here is a chart and brief article. Relative Weight Chart