Problem Rat Training

Question
Hi there!
I've recently adopted two new rats, each with different problems, to join our third "widowed" rat.
One, Tegan, is at least a year old and very friendly, but she's a runner. If we put her on the couch, she immediately runs and hides in the most difficult and, sometimes, dangerous place she can find. Like I said, shes a sweet rat, she's friendly, but she's got some sort of fatal attraction to the floor.
The other, Piper, was born about 4-5 months ago, and the litter wasn't socialized much. At first she was shy and mostly stayed in her hut, but she'd take a treat or two. Now she's basically unresponsive. She is not curious or playful. She barely moves except to eat or drink. She doesn't really move at all. We put her in isolation in a smaller cage to see if we could get her to interact yesterday, and we're trying to do trust training with her, but, like I said, she's unresponsive. We've had success with "problem" rats before, but I'm at a loss with both of them.
We got both rats from a small animal rescue that was a bit overloaded about 2 weeks ago. They never fought with our old rat and have never even tried to bite us, so they seem to be just behaviour problems rather than a more serious issue. Other than that, both are healthy - eating, drinking, pooping as they should, no obvious health problems.
Any help in training these lovely girls into good rats would be appreciated.

Answer
Hi Steph;

I could give you MY answer on this, but a better, in-depth answer would come from Sandra Todd. Sandy has a TON of experience dealing with these kind of issues; and I respect her quite madly as an official "rat trainer". I suggest posing this same question to her. You'll have a more clear idea of how to handle it from her. :)

Best of luck!