Ferret trouble please help?

I have two male ferrets they have both come from the same litter, they are 9 moths old now, and iv had them since they were 11weeks old! Recently there has been a squealing noise from the hutch and on a few occasions one has the other by it's neck making a reddish mark I bathed them both once as they were really smelly and the redish orange colour came off with no cut or bite marks... Are they fighting or just plain rough I'm worried there going to hurt each other... Please help any advice wud be great. P.s. When I take one out the cage the other goes mental and wants his buddy back but they look like there scrapping with each other when there together???