Hey there!
This is most likely a genetic mutation (completely normal!) or a little bit of wind damage. Just make sure your fan isn’t blowing directly onto the plants, I’d point the fan a little bit above the canopy so it is circulating the air above but it isn’t completely disturbing the leaves of the plant. Once she gets a bit bigger you can definitely have more direct wind to help strengthen the stalks but it’s not necessary and just an option some growers use to strengthen their plants.
Good luck!