I have a 6-year-old Japanese bantam hen that has been progressively declining over the past few weeks. Her comb and wattles became pale, her skin began yellowing, and now she has developed a very rock-like crop. Her crop isn't swollen or large, but it is very hard (and not much is passing). She is not eating unless hand fed. She will no longer drink water, either. -very lethargic. Is this potentially just age-related?? All of our other birds are healthy and thriving. -no sneezing, discharge, or any other symptoms.