I have a Red Star hen that has been acting unusual this week. Two days ago she was not herself, just stood still there until she laid a strange-looking soft shell egg. I thought she is low on calcium, so added exrea oyster shell in thd feed. Since then she looked sick now and then, usually she is active all the time, eat and scratches in the yard. But this week there are times she just stayed still, looking lethargic. We added Corid in the water since yesterday, she is still not well. Yellow foamy poop, please see picture. Please advise, is Corid the right treatment and how soon do we expect to see improvement if it is coccidiosis. Is this related to the egg issue? Should we try antibiotics? Thanks very much,