I think only one dome of each type works at once, but e.g. multiple Air domes can be stacked so that even if a spell gets through, there will be a Dome up to block other spells cast at you later that turn.
what about simultaneous spells though. if multiple rituals target a dome of air in the same month, and one destroys it, does the air doem still negate all the other rituals or?
and does a dome take effect in the turn it is cast or only from the turn thereafter?