Assuming you have an older property and the outside of the wall is directly exposed to the weather it is normal for the softer bricks to crumble. You could cut out individual bricks and replace them but do use a similar mortar mix to the existing.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!