I read high fiber diet can cause constipation and potentially anal fissures + diverticulitis from passing large stools. i recently passed large stools after starting 30g per day fiber. should i worry?

No: High fiber diet if tolerated is fine. At 27 it's probably a great habit.

Fiber + fluid: In order to avoid hard stools after starting an increase in fiber intake, increase water intake as well. Chronic passage of large hard stools can produce anal fissures and hemorroids, but it is not uncommon to pass a larger soft stool when initiating a higher fiber diet.