I bought one of these plants and seperated the smaller ones and re-potted all of them. I'm not completely sure how to care for them and they're not doing too well. Can someone help?

The most important thing to know is that they do not like to be in soil that stays wet too long. I expect that you used a free-draining mix of the sort in which you would grow cactus. When you water, do it thoroughly, but then wait until the top inch or so of the soil is dry before you water thoroughly again. This shows you that the roots have used up the water in the soil, opening all the spaces that hold air and letting the roots breathe.
For your small plants, I would suggest waiting (after you make sure that the soil is moist) to see some sign of growth, or at least to see the leaves looking good. One thing ABSOLUTELY NO FERTILIZER until they start to look good - that probably means next spring. Derek