Lead core can be deadly on trout. I've used down riggers with not much luck but really nailed them with lead core. Couldn't buy a strike from landlocked salmon on a remote lake in Maine using my portable downrigger. Leadcore worked though. Congrats!
Sorry to hear no holdovers though. Years ago we used get at least one 18 to 19 incher among this year's stockers within a day's fishing.
There is a possibility the holdovers become more bottom oriented. The largest browns tend to be bottom oriented from my experience.
Or the survival rate for holdover is low in August to September due to depleted oxygen. Browns can handle that better than the bows.
I can't imagine they are being fished out although I did run into a lake resident that was bragging about going back out over and over to keep stockers well over his limit. This was on Facebook and when I chewed him out for it he changed his story. Still reported him.