Same here! I noticed one of my two year old hens having some this morning.There's no sign of blood (thankfully), and other than cecal poos, I haven't definitively seen this with any of my other (seven) hens. Mine all eat a 50/50 mix of Kalmbach All Flock crumbles and Kalmbach Henhouse Reserve, with a treat of mealworms in their toys (they kick them around and treats are dispersed) every 3-4 days. Food and water are available in the run full time, but only accessible from 6:30 am-7:40 pm (they're in their coop with no access overnight). Our coop is raised, and the covered run is wrapped with 1/4" hardware cloth with a buried skirt 18" deep & another 18" out from the edges of the run structure. Our weather in VA has been all over the place, bouncing from 40-85° over the last couple of weeks.
Sorry for the wordy post. I was trying to cover everything I could think of.