Why is Maple Suger so difficult?

Several years age I bought Hibiscus acetosella "Maple Sugar", knowing it was an annual. Before night temps got too cold I moved it indoors to a sunny window. Did fine till about Xmas, then began to die from the bottom up. I took cuttings that did well for me. They spend the summer outdoors. I keep it for the foliage, it rarely blooms for me, but when it does its in the house in early winter. My question is, why will one thrive through winter and the pot next to it insist on dying? Can't keep them going long enough to get a nice big one. Any one out there have any experience with these lovely hibiscus?

I've never grown those indoors, but with any plants that are having troubles, the first thing I would always suggest checking is the watering, make sure it's not getting too little or too much (too much is a more common problem, but the symptoms of too little can be similar). Before the next time you to water, try sticking your finger down a couple inches into the pot and see how it feels--if it's still pretty wet then you're watering too much, but if it's bone dry then you're not watering often enough. Two plants sitting next to each other may not have exactly the same watering requirements because of different sizes of the plant and/or rootball, whether one is getting a draft and the other's not, etc. Another common problem for plants being overwintered indoors is heating vents blowing directly on them--I would also check for that. Cold drafts from not-so-airtight windows (or from being near a door that's opened a lot in the winter) could also be problematic in a really cold area like yours.