Such is in the life of clowns...Your tank is a 75g if its stocked with
LR hopefully he can hide out...
Clowns of even size will scrap and most times never pair, if his fins are getting nipped bad news here!!!
I have had success pairing clowns by buying one slightly smaller, Placing him in the QT may make it worse as when he goes back alpha clown may fully own that tank....
Percs are not all that user friendly, if you wish mulitple clowns maybe you should go with Ocellaris Clownfish
I would bring the clown to health in qt and return him.