Chapter 14: The Tragedy - S2-E6
Other mistake: Ahsoka tells Mando the name of a planet. Just the name and nothing else, we see him take off. It's a rather big planet as we can see from the atmosphere, and the Jedi temple is secret...yet Mando right away just finds "the big rock" in a planet with a complex sorta Earth-like geography.
Chosen answer: They could be just like wrinkles from age, like the elderly Togruta in the Zygerrian slaver arc in The Clone Wars series, as Ahsoka is considerably older than her animated appearances. I think there is probably a character design/stylisation aspect to it as well - the other Togruta we've seen in live action, Shaak Ti, has four segments or folds in her lekku that were not visible in her Clone Wars appearances, so it would seem the character design in Clone Wars and Rebels reduces such features.
Sierra1 ★