Are you giving them plenty of room so that leaves do not touch other leaves?

I have lots of Robs and the only ones that give me trouble are SMARTY PLANTS which grows with leaves hugging the pot and one other. For the most part they grow quite flat. Hot Chocolate grows flat for me.

Nancy

I grow under lights too, and some of my plants sometimes exhibit tight, twisted leaves. I think you may have too much light for those particular plants, not too little. I usually move plants showing these symptoms toward the edges of my lighted area so they get less light. Usually the lower light level will allow the center to loosen as it grows out, and the leaves stop twisting against one another.