If it seems to you that your spouse is stressed or concerned or not their usual self, notice and say something. Don’t just hope and assume that it will resolve itself. Ask – with care and concern, “I’m noticing that [you are more quiet] in the last few days. What is going on for you?” “Something is off. I’m noticing that you are going to your [stress-relieving mode]. What’s going on?”
Listen with concern and humility. Do not dismiss it with a quick “it will pass” or “calm down” or “everyone goes through that sometimes”.
Ask what kind of support they would like from you. If they want practical support, try to be that for them. If they want emotional support, be that.
Check in often as together you work through whatever is going on for them.