Overwatering can lead to root rot and prevent the roots from absorbing oxygen properly. This can result in curled and droopy leaves. Make sure you're not overwatering your plants and allow the soil to dry out between waterings.

On the other hand, underwatering can cause leaves to curl and become brittle. Ensure your plants are receiving adequate water and monitor the moisture level of the soil.

Cannabis plants prefer specific temperature and humidity ranges. High temperatures, particularly coupled with low humidity, can cause leaves to curl up as a protective measure. Similarly, very low temperatures can also lead to leaf curling. Maintain suitable environmental conditions within the optimal range for cannabis cultivation.

Nutrient imbalances can cause various leaf problems, including curling. For example, nitrogen deficiency can cause the lower leaves to curl up, while excessive fertilization can result in overall leaf curling. Use a balanced nutrient solution and ensure you're providing the appropriate amounts of essential nutrients.

Infestations by pests such as spider mites, aphids, or thrips can cause leaf curling. Additionally, fungal or viral infections may also lead to curled leaves. Inspect your plants regularly for any signs of pests or diseases, and take appropriate measures if necessary.

Too much light, particularly in the flowering stage, can cause leaves to curl up or "taco." Ensure your plants are receiving the appropriate amount and intensity of light for their growth stage.

It's important to closely observe your plants and consider these factors to determine the specific cause of leaf curling. Adjusting the environmental conditions, addressing nutrient imbalances, and taking appropriate pest management measures can help restore your cannabis plants to a healthier state. If problems persist, consulting with experienced growers or professionals may provide further guidance.