We've had a chicken that's been a bit down in the dumps lately. She is second on the pecking order. Her sister, who is the third and last, has seen an opportunity to get up and take her position on the order. Consequently, she has been randomly attacking the unwell chook and we've had to separate the two. The top chook joined in the first attack but doesn't seem to anymore. This has been going on for two days now. Any ideas?