Not sure on your due date for hatch but could be any of your options listed....only suggestion I have is a bit of Vicks (or menthol type tooth paste) rubbed under your nose, get a nest worth of fresh straw and gloves....lift broodies chests up enough to see under them, if you see broken egg or poo you will need to remove the hen from the nest, pull the eggs and soiled bedding, replace with fresh bedding, put back eggs and let broodies back in. It is a nasty job but not doing it means the other eggs or hatching chicks will be exposed to the bacteria from the mess and may die also.