Curling fan leaves, nothing obvious, any ideas?

Heat

High BeanieBoo, The taco leaves are as you mentioned already the result of heatstress. Good job on spotting it early and moving your lamp further away from your plant. The leaves wont just recover and go back to the state as before the heatstress. Don't worrie about it as long as it doesn't het worse. Your plants look healthy and because you solved the issue before it became a problem it will not effect you grow. Happy Growing! 😋

This can be a couple of other things - but with no diary, it's hard to give a SOLID answer... anyway, it could be overwatering, underwatering, heat stress... please start a diary so we can have more information! It helps us help you!

Excess moisture and heat can cause your pot plant’s leaves to curl up. Overfeeding can lead to your plant’s leaves canoeing up, wilting, and producing low-quality buds Doubt it's heat stress if you see your cannabis leaves canoeing up along with the presence of yellow-brown spots on leaves. Too much wind can cause your plant’s leaves to cup upwards. Wind-stressed cannabis plants curl up their leaves to protect themselves from strong winds. Good luck 👍