Terrible Two's?

I could really use some advice from other mamas of little ones. My daughter is two and a half and is usually pretty well-behaved. She eats well most of the time, and is happy to read books, play with her kitchen or toys, etc.

But for the past week or two, she has been very difficult. She refuses to eat almost everything we put in front of her, even her favorite foods. She is also very whiny and has tantrum after tantrum all day long. Hubby and I are so frustrated by this!

She is getting plenty of sleep and not showing any signs of illness, so I don't think those are the culprits. Does anyone have any ideas of why she has suddenly turned into a very difficult child and how to get her back to normal?