@Stick, I used a new fresh pack of already - nutritional soil. No extra nutrients were used. It's not root bound, I had checked it. And I don't have the tools to check the pH and EC. I've noticed that the midribs at the point which the curling starts are brown. I've also noticed some very small bugs (one brown and one smaller white) from under the leaves that looks slightly like lice under microscope.
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