When the the serrated edges of marijuana leaves curls or tipped up like that, it's often a sign of temperature stress, over watering/root problems or extreme humidity levels.
When the problem is low humidity, the leaf will also often fold in the middle, like a taco.
What's your temperature in your grow area? Is there a hot spot around these plants from the grow light?
If this is happening to the plants which are closest to your grow light, that's a hint that the problem may be temperature related.
If your light is simply too close, you can move the bulb further away from these plants and this issue may resolve itself. However, these leaves are showing symptoms of heat stress, without light stress (burning / spotting), so it's more likely that the light is a good distance away and the heat just isn't being controlled properly.
If plants are also droopy, it's likely you're dealing with watering or root problems.
Good ventilation and an exhaust fan will go a long way towards preventing all these problems. If the whole grow area is too hot with stagnant air, you will want to consider venting out all that extra heat.
Having good air movement, like a small fan in your grow tent blowing over the tops of your plants, can help prevent hot spots from forming directly under your grow lights.
In general, if it's too hot for you to be comfortable, it's too hot for your plants
