This is weird. I got a whoops,fart, fairy egg today and loads of people seem to be discussing small eggs!
It's the white speck on the left if you miss it! I don't think it's necessarily something to worry about though.
I'm with aart - beginning of a laying cycle, new layer, old layer or probably with your girl the end of a laying cycle. She may be gearing down to take a break. Why ? A lot of conjecture about this. My theory - it just happens.