The Smartest Mice in the World
Are you using pelletized rodenticide? If so, they may be stashing it and eating it later. That may explain the dead mouse in kitchen. I don't use pellets for this reason.
Place bait blocks above drop ceiling in basement or otherwise get it up on top of the foundation wall. Also, if an attic, even if it is a crawl space/hatch door, at least throw bait into the attic if you can't get in easily. Also bait behind kitchen stove, always a good place to bait, and safe. If attached garage, get some bait out there, too.
Realize also that re-infestation can and probably is occurring. Keep fresh bait in place even when no activity noticed. Better to kill 1 or 2 as they get in, rather than 6 or 10 all at once.