They might have been burned out. At the stage before your body prevents you from getting physically to work your work output takes a very serious nose dive.
Lastly, not sure how them being burned out would changed all that much. The impact on team would be all the same.
But sometimes, laziness is the thing.
My original point was meant to be that as long as you think about out productivity, have somewhere back in your mind that something should be produced today, you are fine and not in that worst performer category. Because you are trying and that will keep you away from such fall. It was meant to be reassuring in some way.
But, sometimes, laziness really is the thing.