Lactuca Serriola, that's it! Good to know it's not poisoning them. They do have free access to layer pellets and water.
It hasn't been hot yet - temps have been fluctuating between 60 and 90 degree highs over the past couple of months. Next week it's hitting 100 for multiple days.
Game cam arrived today, and I set it up to take pictures of the top layer of nesting boxes. It was supposed to take a picture every 10 seconds, but instead it was going off every 14-16 seconds, with random skips of 30 seconds, 1 minute, or even a few minutes. WTF.