(I won't comment on specific creature's immunity or resistance to specific attacks, but I will note that the charming affect of Unearthly Chorus fails against creatures you're attacking. I'll go with your original submission)
Roberts steels himself against another round of attacks.
[Second Wind: d10 (5) + 2 = 7 HP]
Snerp casts another round of vicious mockery against the southern ghoul but it resists.
The ghouls continue their onslaught of Roberts, but only one manages to score a glancing hit and Roberts shrugs off the unholy affects.
[Roberts takes 4 slashing damage]
[Constitution Save: d20 (16) + 2 = 18, Saved!]
Grahf flings three more radiant bolts, and the bloodied ghoul, and it collapses from its wounds.
[Magic Missile Damage: d4 (1) + 1 = 2x3 = 6 radiant damage]
With a ghoul out of the way, Roberts more easily focuses his attack on the second ghoul, dealing a minor wound to its arm.
[Melee Weapon Attack: d20 (17) + 5 = 22, Hit!]
[Longsword Damage: d8 (1) + 3 = 4 slashing damage]
In concert with Robert's attack, Eikka follows up with a heavy blow from her mace.
[Melee Weapon Attack: d20 (17) + 2 = 19, Hit!]
[Mace Damage: d6 (1) = 1 bludgeoning damage]
Combat Summary:
[22] Snerp - 12/13 HP - 13 AC - Bardic Inspiration: ⭘⭘ | Spell Slots: 1⬤⭘⭘ [Bardic Inspiration]
[15] Ghoul 2 - Injured
[15] Ghoul 3 - Uninjured [Turned, 8 Rounds Remaining]
[11] Grahf - 14/14 HP - 10 AC - Spell Secrets: ⬤ | Spell Slots: 1⬤⭘⭘
[9] Roberts - 7/20 HP - 19 AC - Action Surge: ⭘ | Second Wind ⭘
[1] Eikka - 12/17 HP - 16 AC - Channel Divinity: ⭘ | Relentless Endurance: ⬤ | Spell Slots: 1⬤⬤⭘