Growing tip curl

I'm posting because I have plant with a pronounced curl to the new leaves. See the photos.

I've tried researching this exact effect but couldn't find the same problem addressed on outdoor in soil plants. All I found was regarding indoor grows. It just didn't seem to fit to my specific problem.

I've grown this strain for about 4 years and never have seen this in my garden on any strain before. This is a hybrid and also from a feminized seed. It's called Bisho Purple from Tropical Seeds in Spain. It's growing in a hole I grew the same strain in last year. I have two other plants of this and they are normal. Flat healthy leaves with no curl at all.

This plant is a little darker green and has a rougher texture to the leaves and a slight yellowish discoloration. There's also a slight reddish rust coloration in the center section between the veins of the leaves which is visible in the closeup photo. One person said they thought it might be virus but couldn't say which one or advise what to do.

Since flowering is just starting I'd like to see if I can address it now if possible. It seems like yield will be reduced by this so if I can fix it that would be great.

The idea that the plant is trying to slow down photosynthesis by curling just doesn't quite adequately explain this in my view. Something more is going on with this plant but what exactly?

Thanks for any advice. I hope there is someone here who can diagnose this from past experience.

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Because you say the affected plant is growing a hole that was used last year I would be suspicious of a mineral imbalance. So I would treat the growing area with Gypsum.

Perhaps two clenched handsful per square meter.

There will be short term yellowing of the soft growth which will grow out with watering.

Perseverance furthers!

Water stress, especially from dry conditions or excessive heat, is the primary cause of leaf roll on plants. Keep the top inch or two of soil aerated well with a hand cultivator between waterings and water deeply. Don't put any lime on your plants because that will cause more harm.
Just to be on the safe side! Pests like aphids, thrips, mites and whiteflies cause leaf curl on plants from their feeding activities. Take a magnifier and get a close up to make sure you don't have bugs.

Thanks for those suggestions. I've never encountered pests like aphids, mites etc. And no other plant shows any signs of this. I usually spray natural insecticides like Spinosad and Bacillus Thuringiensis which has pretty much seemed to work. I will take a close look and see if I can spot anything. Usually the only really destructive pest I have is caterpillars. They chew up the stems inside the flowers, ruining them.

Maintaining healthy plants over the 6-7 month grow cycle is tricky here. The soil is a sandy clay that needs regular additions of organic material to increase aeration and help drainage. Drainage is a problem here too. This site sits on only about a 30 cm (15 inches) of soil and under it is clay and limestone. Watering is tricky. Too much and the lower roots can't breathe. Too little and the soil biology dies at the surface, even with mulches. It's a difficult balancing act and I wish I had a better site but this is what I have.