My two Guinea Pigs have lived together with no problems for four weeks now, or thereabouts. I'm giving their cage a big clean this morning and when I've taken them out into the other cage they are behaving very strange and it seems to be getting worse 
GP1 who is the more dominant has started trying to mount poor little GP2 and rumbling really loudly at him, they've also seemed to run towards each other, more to butt each other than fight IYSWIM.
They also jump and twitch wildly around the cage, I'm not sure it's "popcorning" because it seems quite frantic and they sort of twitch their heads when they do it too.
They are still small but I'm worried it will get worse if I leave them together. Any advice would be really appreciated as I'm thinking of separating them.