It's not uncommon for a home's foundation to settle slightly with time and develop some cracks. Foundations also develop small surface cracks sometimes shortly after being poured or built. The vast majority of times, they are just surface cracks and can be easily filled and patched with no further issues. You can use an epoxy to fill the crack and close the gap to water infiltration. Then, apply the surface treatment (stucco, etc.).
Multiple Doors Out of Plumb
If you have several doors in your home that are out of plumb and/or not functioning properly, it could be an indication of a structural issue in your home that has caused excessive settling. It may be that the doors were just poorly installed, but if many doors in your home are having issues, you should do some investigating to see if there are any potential structural problems.
If you notice water seeping through your foundation walls in the basement or crawl space, or even very damp or moist walls, you need to address that issue promptly. Water infiltration of your home's structure can cause serious issues over time. First, check the grading around your foundation. If your yard slopes toward the house anywhere, you may just have a grading issue and need to create a slope away from your home. If that isn't the case, you may need to have the foundation walls waterproofed and/or drainage installed around the perimeter of your home.