I have tomato and potato leaves curling as a fern would. This happened while under the grow light in early development. The tap roots of the potatoes are also curled back to the top. I have not used any fertilizer on these plants.
Tomato Leaf Curling as a Fern
Certified GKH Gardening Expert
It is very possible that the weather is the cause of this, but it is also possible that it is tomato leaf curl (which can affect other nightshade members as well, like potatoes). If it is the weather, it will clear up but if it is tomato leaf curl, there may not be much you can do. This article has more information: https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-leaves-curling.htm