Pics are dark and fuzzy to clearly see but if its the feces you are concerned with, this happens when there is excess much in the stomach/intestinal lining and will fall off. Often approaching fish with net will allow it to fall off as well. If youre feeding a bit of mysis or brine shrimp- this will be a cause in Some cases.
Add TDO pellet food as well as LRS fish frenzy to the diet