Where did the fish on the fire of coals come from in John 21:9?
They did not come from the disciples' net. When the disciples reached shore, the fire of coals already had fish laid on it; everything was already prepared. So the fish on the coals were supplied independently of that miraculous catch.
Les explains that when the disciples came to land, they saw a fire of coals with fish already laid on it. He asks where those fish came from and answers that they did not come out of the net. The net held the great catch of fish, but the fish on the fire were already there. Les emphasizes that everything was already prepared. This is set in the scene after John recognized the Lord and Peter cast himself into the sea, while the other disciples came in the little ship, dragging the net with fishes.
As soon then as they were come to land, they saw a fire of coals there, and fish laid thereon, and bread.