I bought a haworthia retusa a few weeks ago. All of the leaves were nice and plump. I read that you should water it sparingly in the winter so I wasn't watering it for fear of overwatering. But then I noticed the leaves were shriveling up. I watered it a little bit, and didn't notice an improvement. So last week I gave it a good water, but that didn't seem to help. It still looks like this. Any suggestions?