Don't let it dry too much, keep roots warm and give it plenty of light.

were they green and crispy? Also how big are these plants? pot size? Had that happen to mine. It took close to 2 years for it to recover. Now looking sharp!

No, they were soft and green. They're pot size. That's why I think they're not beyond saving, since the leaves were just drooping, not completely crunchy yet. Of course, there's no leaves anymore, but maybe some of the root system is still there

Can anyone tell me what the right care for these is? Should I keep them on the mat or keep them cool?

It will not hurt to keep them on the heat mat and may benefit them.

The problem may be Winter Leaf Drop (WLD) caused by cold roots not being
able to provide the tree with nutrients and water in amounts that
the tree needs because it is actively photosynthesizing.

To minimize WLD:

· Irrigate with warm (77 – 90F) water

· Decrease amount of light

· Maintain root temps at 59 – 64 F

If WLD continues, increase root temp to about 70F

The above information from:

http://www.steffenreichel.homepage.t-online.de/Citrus/lime2.pdf

http://tropicalfruitforum.com/index.php?topic=13332.0