Expecting your partner to read your mind is not the way to have a healthy relationship. When you're with a good partner, you should be comfortable enough to address your problems with them or ask for a shoulder to cry on as needed.
Of course it's nice if a partner notices and inquires. Your problems are your own to tackle though.
Edit:: It's specifically the acting different because they're in a bad mood that I was referencing. If you're in a bad enough mood that your partner notices but you haven't been honest about why, it's not on your partner to sus that out. It's on you.