I have a marans/brahma cross hen, 2-years-old in May, behaving strangely. She goes into the nesting boxes, sits there, then after a while, gets up and leaves. There's never an egg in the box. Looked up internal laying, and the only symptom she seems to have is a slightly swollen area around her vent. She's active, eats well, dust bathes and generally loves life. There's no cure for internal laying, is there?