Poor plant!
Alcran, you have to understand that though they are intermediate to highlands, they are not going to be able to tolerate freezing temperatures like that! Please get them back in!
I think that a more gentle (yet still radical) approach to mites is to soak the whole plant and pot in water for 4 hours!
Also very weird that your Ventricosa doesn't have as lancellate leaves as what I think they should, maybe it's a hybrid? Or maybe adaptation to colder weather, not sure!
TTFN
Arvin