SMB=Swiss Merengue Buttercream
I always coat the RKT with melted white chocolate. Once it hardens I coat it again. You can rub the chocolate smooth with the warmth of your CLEAN hands!.Then cover with either fondant or...
Perhaps the whites were warm and melted the butter? Next time try putting it in the fridge for about 15-20 and whip. That should help.
This is the recipe I use. It is from Sweetepolita and it has not failed me...
I am an icing images fan for life. I've tried Lucks and found that Icing Images sheets are more flexible and stay that way longer. The ink dries almost instantly and the paper has a yummy scent. I did not have such great luck with Lucks.