Yes, but that's normal. Avocado oxidizes quickly due to the healthy fats found within them. The more air that comes into contact with your avocado flesh, the faster it will degrade. That means you'll want to keep any leftovers tightly wrapped up and store them in an airtight container as quickly as possible. It's also important not to leave your avocados out of the fridge for too long since they are sensitive to bacteria. If your avocados have been cut or sliced, don't leave them out for longer than 2 hours. If you're planning on eating them later in the day, pop them into a container and back into the fridge until you're ready to use them.