That plant looks reasonably healthy for this time of the year. Why do you think it is dying? My marginata has three stalks of varying heights and the tallest one has been loosing leaves. Also edges of the remaining leaves are yellowing. I am chalking it up to it plonking a couple of times late fall in the rain/move indoors from the outdoor open balcony. I don't think there's need for alarm (in either case, yours or mine). I would be sure to not overwater or feed it during the winter months.