They would have established the pecking order within a few days after the head hen died. You may have to watch, but there's a leader there somewhere.
Provide Oyster Shell free choice for your hens. The feed is probably o.k., 16% layer feed is what a lot of folks feed. Not sure about Calcium supplements. Generally the hens *should* get sufficient Calcium from their feed and supplemental oyster shell. When and IF I give a Calcium supplement (usually Calcium Citrate) it's only when a hen is in clear crisis and she only gets it for a short period of time (3-5 days).
If you provide electrolytes, do be sure to provide a water station with plain fresh water too. While electrolytes can be helpful during stressful times (hot weather, an attack, etc.). Imho, they do not need to be provided most of the time.
Prolapse can happen for a number of reasons, a few things come to mind = straining to expel a large egg, dehydration, excess fat in the abdomen (fat takes up room/hard to expel an egg), genetics, poor diet, not enough calcium, constipation...many many things can happen to cause a prolapse.
Nice coop!
