I'm not sure if this applies to Red Knees as well, but from what i've noticed with the care of my desert tarantuals, they mainly require plenty of hydration. We picked up a tarantual who looked like it was about done on the side of the house, and when we put it in a tank with a platter of water, the tarantual looked as if it was literally soaking itself in the platter (legs stretched out and all). After about a day it seemed to regain some of its energy just fine.

Like I said, i'm not sure if this applies to Red Knees, since I know they come from a completely different climate than any desert tarantuals do, but I figure that at least they need some method of hydration to get their energy back.

Best of luck with reviving, I hope something can pull through!