Option 1) Slowly build up your expectations of their output over time. Be subtle about it, so they don't feel like they're being burdened. They'll adjust and rise up to meet their new expectations with little effort. It's non confrontational and gets results, albeit gradually. Option 2) Explain to them, first in a meeting and then individually if and when needed, that expectations have changed. It's their job to meet them. If they fall short, performance action plans will have to be implemented. You'll make waves, but people will know immediately and with no uncertainty what is required of them. Option 3) Do nothing. Get frustrated. No matter what option you choose though, encourage, reward, and support every step of the way. If you don't have their backs, they won't have yours.
Option 1 sounds like the most feasible for my position. It's just such an odd dynamic I've never been in before. It's just this one team that has the mentality, where everyone else is back up to speed. But my frustration some won't fix it. I'll calm down over the weekend and try something simple in Monday.