If a person lacks a technical skill, there are various sources of knowledge readily available depending upon what your budge is - books, online books, seminars, etc. These are easy to identify and packaged solutions are available to address the situation and remedy them. Non-technical skills like language, communication, etc are more difficult to address, and usually take longer to remedy. But the most difficult area to remedy is that when the intent is lacking. The individual is not passionate enough to do what it takes to get the job done.

In any case, you have to address the situation immediately.

Waiting to address the situation will have various consequences that will be destructive to your organization. If you condone certain behaviors, you are in effect encouraging them. This will send the wrong message to your team. The other team members may not copy the incorrect behavior, but they may be grudging the fact that others are getting off easily. This will sap the team spirit and lower the morale.

Some of your corrective actions may bear positive results and others may not. When you have done your part, and you don't see the desired improvement, you may have to let the person go. When you do so, don't be hard on yourself - you have done your part and done what is right. Treat the individual with dignity that every person deserves. Also realize that you may be doing the person a world of good by giving them an opportunity to find a place where their skills are appreciated. That will help them in the long run.