I'm going to ask a co-worker to pick up the pace
Why do you need your coworker to increase their pace?
They've been wasting so much time, and I wish they would pick up the pace.
It can certainly be frustrating to work with someone who is slower than you, but you should reconsider rushing them. If they feel forced to speed up they could end up making mistakes or getting injured.
Perhaps the problem was caused by an injury and they can't do as much work. I'm going to ask for a doctor to check it out.
Asking a doctor may not be a bad idea. You want to try and be understanding towards your co-workers before simply rushing them. If they are really not up to going faster, rushing them is only going to cause more issues.