i would get them outside now and keep your eyes on them.if you can give them a slight tug and they still hold on there is hope.if you gently scrape the bark and if its wet and greenish there is hope.ive seen one of these have the top chopped of and grow new shoots from the base.

I appreciate the feedback, however I wanted to clarify that I live in MN and it's still a cold winter climate here. I was wondering if you still think outside is the best thing for them at this point, or do you have any other ideas for how to help them survive indoors until spring?
I'm also not sure how much more sun/water/fertilizer will help once they get to a certain point. I know this probably sounds silly, but how do I know when it's too late and I just have to buy a new one? The one looks so bad, I'm wondering how I could help it to grow new shoots from the base, as you mentioned. Otherwise, I'm afraid it doesn't have a chance, because the old branches are all gone.
Please advise,
Thanks!

ow sorry no your just going to have to cut the old stuff of and hope for the best . you can easily overfeed and these dont like being over waterd.you mite of lost them but time will tell.take care bye for now.