Norkali....I don't know much about cold temps and plants.....never had the issue so don't really know what it would look like.

I'm having ALOT of trouble getting a good idea of how your plants look with that HPS light yellowing and mylar reflection in the photo. I'm NOT a soil grower so a better photo may not help....but I can't really even see the leaves very well in that pic. Any chance we could get a better one?

And what is the ph of your water and soil runoff?