Leaves turning dark purple and almost black what's going on?

Fall colors showing off LOL

I agree with the PH too low. To low of a PH can cause molybdenum deficiency. It's rare but I think in your case it just might be. If your PH is ok on your pen, it might need calibrate.

Judging by stems and just overall appearance. She is starving. She has been eating stored nutrition in leaves causing the fading color morph. Substrate ph could of crossed over to a lock out.

All strains have anthocyanins (pigments) in the blue/purple spectrum. Once a plant nears the end of its life and when night temps are cool, that particular plants chlorophyll, which is green, can not "compete" with the blue/purple pigments as effectively, meaning the green colour can no longer mask the underlying blue/purple pigments and this is why the leaves darken, much like fall leaves on deciduous trees. It is nothing bad. If you are keen, go to my diary "cannabis conundrums" and in week 7 you will find pictures of nearly black plants that I grew outdoors mid winter for a bit of fun. They show examples of extreme anthocyanin build up due to limited sunlight being able to support healthy chlorophyll levels any longer, a similar situation to what happens in some strains once flowering gets to an advanced stage. There are also some strains that have a genetic dominance for anthocyanins and will even be purple in veg and produce purple flowers, notably strains from Pakistan and Afghanistan. Hybrids with these genetics may also carry dominance for purple leaves, no doubt the strain you are growing does too. Hope this helps, Organoman.

Ph is too low, 6.3-6.8 is a much better range. You wrote 6.0 in the diary. Probably locking out P or K is my guess. Also that’s a awful lot of different feeds in that nutrient line up. I would switch next time to a more simple company/brand. That’s just my humble opinion brother👍 Ignore the text book info guy commenting with the massive paragraphs lol

Here's a few differences in grows and the different appearance but the same strain. growdiaries.com/diaries/132139-grow-journal-by-mr-weeds-autos wk 5 so many terps. growdiaries.com/diaries/125271-grow-journal-by-smoking-hills9/week/719657 To harvest barley any terps. Different cond play a factor aswell as the amount of anthocyanins, some plants like purple punch have enough to change the plant but a different strain grown in same cond wit little anthocyanins will show badly if none of them types of fantastic colors and terps. Like gold leaf has thst right amount of stuff and whatecer you did plsyed a factor 2. Great looking grow.

Some strains have what's called anthocyanins. Which is effected by temp drops, stress light changes, espically when in the resting period. It's a good thing. Lots of ppl who buy the purple strains like purple punch don't have the right conditions for it to happen. In no way is it bad or caused by anything wrong you did just the genes of some plants. Well that's what I've learned by researching it the last 20mins cause I'm trying purple punch next and have heard ppl complain about not getting that affect as they got closer to harvest you'll see the bud change purple but the leafs are a rare and harder thing to get. It'll only increase as you get closer to harvest (ppl change temp, stress their plants and so on to get this effect, so ive read on diaries were i seen ppl ask wheres the purple in my strain with that name and so on. T.H seeds have strains that grow black fan leafs some strains just have that in their genes hence their name, but it happens in strains that have higher amounts of anthocyanins, again you have to have the right conditions, ill try pull up ppl who ive seen with names that are meant to have that effect, sometimes there bud might even have very few purple terps and so on when they didn't get that effect you have at all, ive even seen purple punch nearly all green barely and terps. Hope this helps and more so I hope I've your condiotions without causing too much trouble trying to create it, Happy growing

Is it getting chilly where at night?? Kinda of looking like blushing from cold temps or end of life. Good Luck!