You are not describing good performers. A good performer is not someone that knows how to just turn the wrench, it is all facets of work behavior an organization requires in order to produce the best output. This includes wrench turning, of course, but also includes team work, planning, reporting, the politics, communication, reliability, attendance, and so on.

They are exhibiting poor performance. You would not accept this level of performance if this was coming from a widget on a machine; you would observe the shoddy performance and then replace the widget. Humans are not widgets so it is not as easy removing the widget and replacing it with another from the shelf but the concept of remove and replace are exactly the same.

Sit them down and document exactly what work behaviors they need to exhibit, how often, how well, time frame, etc. Document it and make sure it is crystal clear. Since they are contractors, you might have to work with your procurement leader on the exact mechanics of this performance expectation meeting. If after the agreed amount of time both continue to fail to exhibit the desired behavior and performance, remove and replace. It is a project, not an operations; you simply do not have the time nor requirement to deal with employees growth potential as those in operations do. And since they're contractors, you have even less obligation to help them improve. In some circles with contractors, you can cut bait immediately and send them packing.

As the de facto leader, you have to make the hard decisions and do the unpopular things.

You are not describing good performers. A good performer is not someone that knows how to just turn the wrench, it is all facets of work behavior an organization requires in order to produce the best output. This includes wrench turning, of course, but also includes team work, planning, reporting, the politics, communication, reliability, attendance, and so on.

They are exhibiting poor performance. You would not accept this level of performance if this was coming from a widget on a machine; you would observe the shoddy performance and then replace the widget. Humans are not widgets so it is not as easy removing the widget and replacing it with another from the shelf but the concept of remove and replace is exactly the same.

Sit them down and document exactly what work behaviors they need to exhibit, how often, how well, time frame, etc. Document it and make sure it is crystal clear. Since they are contractors, you might have to work with your procurement leader on the exact mechanics of this performance expectation meeting. If after the agreed amount of time both continue to fail to exhibit the desired behavior and performance, remove and replace. It is a project, not an operations; you simply do not have the time nor requirement to deal with employees growth potential as those in operations do. And since they're contractors, you have even less obligation to help them improve. In some circles with contractors, you can cut bait immediately and send them packing.

As the de facto leader, you have to make the hard decisions and do the unpopular things.