changed anything recently? i had same issue long ago, and i didn’t do anything special but eventually it resolved (i only used advice from Marks Shrimp Tanks yt channel, in which he suggested to dip pellets in a solution of water and citric acid, i don’t remember the proportions though). it is said to be bacterial infection but there’s not much information about it online tbh. i would also try tannins
Aniikama5431 
what are your water parameters?
changed anything recently? i had same issue long ago, and i didn’t do anything special but eventually it resolved (i only used advice from Marks Shrimp Tanks yt channel, in which he suggested to dip pellets in a solution of water and citric acid, i don’t remember the proportions though). it is said to be bacterial infection but there’s not much information about it online tbh. i would also try tannins