As for the photo lab, time to find a new one.
As for the bride, it's all about how you make your agreement with the bride in the first place. If you let people know that you can also do minor edits (such as removing small things, or adjusting small things), there's a separate fee per photo that they'd like to adjust, that will surely cut down on the requests later. That's something that most people would agree to at the beginning (especially if you give examples, like removing exit signs, salt shakers, etc). Later, when they ask, you can remind them of the contract that they signed in the beginning, and let them know that you're more than happy to do it at a set price per photo.