Plants turn purple in cold temps with phosphorous deficiency and the leaves curl in strange ways just like yours are. With the pattern on those leaves it certainly looks like deficiency. The plant is pulling nutrients out of those leaves and that's why you see the interveinal coloring and also why the further away the growth is from the plant the more purple it looks.
Genetics can do all sorts of things but that looks like deficiency not genetics
Cold temps make phosphorus less available and you only experience this in colder temps?...
It could be there just not very easily taken up and or it's in a lower quantity so the cold temps are pushing things a little too far; that would make sense based on your statement that at 72 they're fine. "Burnt" tips and edges aren't just a sign of "nutrient burn"...
Just saying
But it is from nuits........ Like I said.
Ideal temps for weed OVERALL is 68 to 72 bud. All over planet earth. Anything higher causes stress in most strains but tropical ones, up to 80. The strain turns colors only at 72 or under, not an opinion. It only changes with a lower temp. When it's summer and it's 74 to 78 degrees, they are stressing or growing under more pressure and stress when they are totally green at those temps, in the last days of flower.
Below 73 is where they grow with less stress and truer to their comfort zone.....So in other words they grow better and healthier below 73 then above factually. With what your saying, I should have problems when they are out of their comfort zone before they are in their best invorment temp wise....Just saying lol.
I'm not asking if I have a problem with my girls, I know I don't..... Been growing this Strain for 3 years now and I know it well....
Just here looking for others who have the same thing going with colors year after year .
Just like FALL with dropping temps changing the tree colors, who aren't deficient, they change colors..... Just like some strains of weed..... Nothing but natural.
The only time I ever burn my tips, just the tips is from nuits. I have never heard of anything else but " Hot soil " burning just the tips. Not
Calmag yellow or brown, nothing like that. Just the tips burnt is from to much nuits from everything I've read and when I ppm up more the 100 PPMs, they get burnt, at just 100 added every other watering they barley burn at all. The more I add over 100 per every other feed, then the burn more. So it's totally obvious when I feed a hair to much and the tips get burnt right before me eyes in 2 days. .....
No problems here as far as I'm concerned, just looking for fall colors is all......That naturally occur in plants Lol. Just saying.