Curling leaves may be symptom of a deficiency in the soil. The new growth at the top of the plant also looks wrinkled and distorted, could be calcium deficiency. It could also be the result of a pest attack, such as aphids feeding. Can you see any insects on the plants? Carefully turn over all the leaves and examine them for insects. Aphids are very small and green and may be difficult to spot. Please update us with what you find?