man ive had exactly the same problem for aaaaages, even worse than yours appears - some of my leaves have done a complete circle at the tips! still yet to find an answer.
this is my first grow, but from the research ive done, posts ive read and things ive tried, personally i have deduced these as the two most likely causes (in my case anyway)
1. over ferting from day 1 - causing nute lockout its whole life. never getting any nutes let alone the extra ones i tried to give it just adding to the problem, causing the leaves to get no help at all. i finally decided to do something proactive about the problem last night by flushing it, awaiting results of this.
2. bad genetics - the rest of my plant is nice and healthy, the leaves apart from being dry and curly, are fine. its budding, slowly - probably caused by the nute lockout.
everything has taken AGES with my grow as well as the curly leaves, and i think that's a combination of the strain being super silver haze, the nute lockout and bad genetics. my seeds were mega mega cheap from a less well known website, 1 of 6 seeds germed.
It seems for me that I have 'killed it with kindness' - its not dead at all its fine apart from the leaves, but that's the expression you know lol. I personally will not add any ferts to my next grow until my plant shows me it needs them - after all, most if not all commercial soils have enough nutes in them already to sustain healthy growth for the first 6 weeks.
And once again the expression "you get what you pay for" has the chance to shout "i told you so".
It's a weird problem though, cos i do have a few leaves in random places that are beautiful, just as they should be. certainly is an odd one. One thing i've tried is trimming off the curled tip of the leaf, just to where the leaf flattens out. i did it at the top of one of my stems, and it didnt seem to mind. perked them up if anything - but i doubt it has any real benefit, and its not a solution to the problem... just looks nicer lol.
Anyway, hope you find a resolution to this, and if you do, let me know man!
