Since he's been moved to new ground it could be coccidiosis, the incubation period is 5-6 days. What do his droppings look like?
Also possible that he was sick with something before you got him, and that's why the others were attacking him. If you suspect coccidiosis then I'd get him started on Corid ASAP.
Also possible that he was sick with something before you got him, and that's why the others were attacking him. If you suspect coccidiosis then I'd get him started on Corid ASAP.