Please help. Twisted dry new growth

hey guys this plant is huge. 7 months veg outdoors in Australia. Grown in a 100Litre pot with coco coir. Fed same schedule and same soil and set up as my other 3 plants.

This plant has a problem, over night or a couple nights the new growth seems to be dying on most the plant, the leave tips going brown, dark grey colour almos blue, feel soggy and some go brown and crispy and dry out completely.

What does this look like, over nute, deficiency, pest problem.. root problem..??

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Leaves have potassium deficiency symptoms. However you also have spider mites and I can see caterpillar holes. I would suggest treating the pest first. There are plenty of pesticides for spider mites, they are very persistent and expand very, very quickly so you will probably need to reapply and be vigilant.

You have spider mites mate :/ I would defoliate lightly to let some air in, and spray with a natural miticide.