Though I am no expert on Frillies, having only been reading about them for a few months on and off but I seem to recall reading you should not breed them till they are about 2 years old. I would separate your two fillies into two cages just to ensure they do not try and mate. I also remember reading that breeding them too young could kill your female as they are prone to becoming egg bound when bred too young. So to be on the safe side, I would keep them separate from now on till they are old enough to breed.
As for them being stiff and inactive, probably is due to the new environment and being outside. I would add some more shed and hides, to give them a better sense of security, even covering one large wall with something solid (bark for climing, sheet of plywood, anything like that). This way they know they are safe from pedators from that direction.
I also recommend doing a search on the frilly thread for more details about breeding, egg binding and humity. There should be some more explainations than I can provide.