Sorry to miss all the "fun" this weekend! It's always hard to diagnose leaves when dealing with home made untested soil and nutes missing major micronutes we feed our cannabis every day. In store-bought quality soil and cannabis nutes you would never see P or K deficiencies until flower, if ever.
Not to mention the cold beyond the covers:
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
"once the air cools to below 18ºC the plant's metabolism" (that's 64ºF)
and
"low temperatures will detrimentally affect the root system and the uptake of nutrients, particularly in the case of magnesium. This micro-nutrient is vital for the proper development of the cannabis plant and if the substrate is colder than 18ºC then this element is most likely not being absorbed by the plant."
If you haven't slurry tested your soil mix, besides raising the house temp I would start there. It requires distilled water to work, and this is how to do it (with a meter anyway):
• Take samples from a few different places where there are roots (dig down a bit rather than just use the top - I often stick a spoon down the outside edge of the pot to grab some from there as well)
• Add an equivalent amount of
distilled water as grams of soil (10 grams of soil, add 10ml water). If that doesn't make a slurry, use enough distilled water to make a stirrable-but-thick slurry.
• Stir it up, wait 15 minutes, stir again. Do that for at least an hour (longer is better), and then put your
calibrated pH stick in the water. That's the pH of your medium.
For soil you should be in the mid to high 6s. Above 7 or under 6 and that will definitely affect how the plant is taking up nutes.
If you have Windows 9, that's the source of your computer issues...Microsoft
went from 8 to 10, skipping 9 completely!
in tackling whatever life has thrown at you.
Yes more than just one. One good thing is it is all old farm land and much better ground for growing than I have now. 
