I've recently returned to collect my plants from my cousin, having been away for a year, and found most of them dead- except for 4 yukkas which i am trying to rescue. (He hadn't watered them and kept them in a cold room). i stripped all the dead leaves off the yukka's and watered them and took them to a light, warm (central heated) room. however, now the new leaves are turning brown and burnt looking. what am i doing wrong? should i stop watering them for a while? or return them to a colder enviroment? I'd really appreciate your help!!