I have a brahma hen with a huge crop- big as a softball(bigger then a baseball). it's very firm and does not go down at night. I'm pretty sure she has eaten the gravel in our driveway. I noticed this 2 weeks ago. does anyone know, will these stones pass or will she eventually starve when no more food can fit in her crop? (she is a bit thin now) she is laying well and eats well,. any advise?