I wouldn't worry about it at all. Good to see you are so 'on the ball' but sounds as though your control is great normally.
I am always within 4-7mmol whenever I check but have had the odd week where things have gone a bit belly up (similar to your experience of late).
I find that things just tend to go back to normal on their own. There does appear to be no reason for it sometimes but I guess sometimes your body can have all sorts of things going on that don't give you obvious symptoms like a cold etc, so just keep an eye on it and don't worry.
JC