Maybe he just got out of the wrong side of the bed that morning? As you've said, he's always been ok in the past.
I used to get constantly talked to about my appearance at work. Despite working in a back office role they had very high standards on personal appearance. If I had a pound for every time I was told to have a shave or do my top button up, I'd be a rich man. Most days I'd get away with it, it just seemed to be when my manager was in a bad mood, or if he had nothing better to do. Sadly he got promoted, and the manager from hell (scouser) replaced him. She seemed to go out of her way to pull me up on things, despite the fact I performed my job above and beyond what was expected of me.
I remember on one occasion she was monging on about my "beard" as she called it.
"Nigel, we've spoken about this before. You are not allowed to grow facial hair on work time"
"it's ok, I only grow it when I'm at home"
If looks could kill

Moved departments shortly after and my new manager prefers men with beards, she actively encourages us not to shave
