Depending on how big the lump is, it might dissolve with soaking the chicken's butt (or chickens' butts) in warm water. Massage it under water and see if it breaks up like a clot of mud would. If it's really caked in there, you might be better off snipping the affected feathers, poop and all...
If you don't provide grit, they may not be getting enough. I would put some out. If they never ever eat it, well, you might be out $6 or so. Cheap (cheep?) insurance.
For my situation, I feed a 20% protein all flock pellet. I have a cockerel, so I don't want to feed a layer feed, which has...
I don't know about the panic eating, but I had a similar experience with poop in the "floof" under one of my pullet's vent. I realized that the ramp up to the roost was so close to the roost itself that she was literally sitting on her poop at night. I took out the ramp, lowered the roost and no...