Sometimes things don't go so well. Sometimes relaxing and having a homebrew doesn't quite do the trick. Sometimes it's not just going to fix itself.
It would be helpful to have some images to compare against as things go wrong. For this community wiki, each "answer" should be a type of issue, like contamination, with an image (or multiple images) that are good examples of the issue.
Note: This is a community wiki. No one will gain reputation for up votes. Everyone can edit every answer