My calla's look dead too.... but always come back in spring
what Becky said about your Asparagus fern
......they need a lot of water leave the pot sitting in a tray of water so it can absorb as much as it needs Remove the brown leaves so only the green ones remain. It's best to do this as fast as possible because rotten leaves will attract diseases.
What turns brown, stays brown. Leave in the same pot till spring. by then it should have roots popping out the base of the pot & mass of them in it ...the fern needs plenty of water although a little less than in summer the. Calla needs none till spring & mango needs only be kept just moist till spring too. just keep an eye on the growing point of your mango, as long as the stem and tip are alive &healthy green in colour, then fresh leaves should form come spring. A cool dry position with good light but away from any Frost