1 Samuel 22:18-19 NIV
18 The king then ordered Doeg, “You turn and strike down the priests.” So Doeg the Edomite turned and struck them down. That day he killed eighty-five men who wore the linen ephod. 19 He also put to the sword Nob, the town of the priests, with its men and women, its children and infants, and its cattle, donkeys and sheep.
After the killing of the priests by Doeg the Edomite there is not much said about retribution and punishment for these killings
2 Samuel 21:1 NIV
During the reign of David, there was a famine for three successive years; so David sought the face of the Lord. The Lord said, “It is on account of Saul and his blood-stained house; it is because he put the Gibeonites to death.”*
But the killing of the Gibeonites is taken notice of to the extent that God punishes the land by causing a famine because of Saul's action.
What was special about the Gibeonites issue?