Drama at the birdhouse

This isn't quite as dramatic as it looks at first glance. While the photos are in the correct order, the chickadee didn't eat the wasp -- it just scared the insect away, with food already in its mouth.

We have chickadees raise babies in this birdhouse on our back porch every year. But this year this one bird (the mom?) looks especially beat-up and scraggly, and has looked that way for weeks. Is is just old, or did something nasty happen to it? Seems to be feeding the kids just fine, though.