Chromis are cool, and I love the schooling effect, but they aren't always as hardy as you'd expect. I have a small school of Pajama cardinals, a six line wrasse, a fox face, royal gramma, and the clowns never bother any of them.
But then, yours seem to have already taken an aggressive stance. Maybe isolate them, rearrange the rockwork, and then put them back while adding the new fish so everyone is on equal footing?
Someone stop me! Please! But... not just yet...
55 Gal Tropical FW
55 Gal Mixed Reef