I'm not overly experienced in Cochin but I have raised them!(one of which is raising a brood of 4 for me ) but Cochin are a very docile breed like the orpington but definitely more cold hardy than heat hardy so summertime requires a lot of shady places and water refills. And during the winter before and after freezing you may want to change your bedding in coop or run as they will make those feathered feet into snowshoes of mud!!! They're not vest observant that I've seen so I'd advise more observative breeds in a flock to watch for danger so the fluffs aren't taken. I had a sickness break out in my coop and hit all my birds but In the end it claimed one Cochin and a Leghorn

two veeery different breeds so I wouldn't say they're any more prone to health risks due to small size. That's what info I have to give! Goodluck on youre hatch