I hate to see a request for help go unanswered so I will throw some ideas out. First, to find 2 or 3 fish dead out of 20 stocked is not that unusual especially if they had their jaw jerked before stocking.

If it turns out you do more than normal post stocking/angling mortality, the first thing I would do is check the water quality. You stated there appears to be plenty of food for the bass, yet they are still skinny so I would suspect something is stressing them. Stressed fish generally don't feed well. IMO you added a lot of fish mass for 1/4 acre of new water. I know new aquariums stocked too quickly can suffer toxic levels of ammonia. Perhaps something similar is occurring in you pond? Low dissolved O2 crashes are also known to selectively kill the largest fish. I hope this helps a little. Good Luck