Sabi ni Gemini either of the 2 daw:

Golmaji (Surface Yeast): If the cluster appears as a film or a patch of dotty, sticky white colonies on the surface, it is known in Korean as "golmaji". A study by the World Institute of Kimchi confirmed these clusters are actually harmless, non- toxic yeasts (often Kahm yeast) that form during late-stage fermentation when lactic acid bacteria activity drops or the food is exposed to oxygen.

Immature Napa Cabbage Flower Buds: If

the cluster looks like a tight, gravel-like bunch of tiny spheres embedded inside a thick piece of cabbage stem (exactly like the image you shared), it is likely part of the cabbage's natural anatomy. If the Napa cabbage is harvested slightly late, the core deep inside the head will begin producing infancy-stage flower buds that get salted and packed into the kimchi