Dark particles from hot water heater

Update on water. After a little investigation, I found that the only place the black particles showed up was from the kitchen faucet, not the bath, or outside shower or inside shower. 4 hours ago I turned the water heater off. Now I see very few particles from the kitchen faucet on the hot water side. I dismantled the faucet and found no problems. Crazy that the particles show up on the hot water side of the kitched when warm and not when cooled off. I will fire up the heater again and see if they return. As always, any help is appreciated.

Thanks