sb can have all kinds of little muations and twists and turns, you my friend have some straight fire phenos, them giant dark leaves are a sign of goodness to come, enjoy man! They look good.
Looks like maybe a feeding of cal mag. Also I think maybe thrips brother.
You said you saw a few gnats. could be the older thrips that means they run a life cycle and the babies are eating on your leaf growth, the young ones particularly like the growing tip.
Thrips you can see with your naked eye. Or you can get a magnifying glass to see easy.
Or do the hillbilly thrip detection test.
Get down to them growing tips close and have a smoke and blow some thick smoke on the tips. If you see shit jumpin off or flyin away you got thrips.