Group content displays in other Groups

Hey folks, apologies if this has already been asked but I've notice something with my set up and I'm hoping its just a simple case of switching something on or adding something to Views.

I have 4 groups at the moment with test content created for Groups A and B. userOne is a member of Groups A and B but when he is on Group A's page he can see all of Group A's content as well as B's and vice versa. This isn't ideal as Group A and B will have nothing in common but there will be valid reasons for granting some users access to more than 1 Group. Any help is greatly appreciated. Thanks