Magnesium is the first to go:
Have you got a heat mat (or two) you can throw in there on end?
The effect of cold on cannabis plants
In this post we show you which methods you can use to avoid the cold in an indoor cannabis crop. There are various modes to keep a stable temperature during the winter so you can choose the resolution that best suits to your indoor or greenhouse crop for personal use.
www.alchimiaweb.com
Have you got a heat mat (or two) you can throw in there on end?