Start the conversation for them. Invite them to say what's up, but don't force.
"Penny for your thoughts?"
"You seem distracted today. Any reason?"
"I hope my friend didn't upset you yesterday when she brought up _____... 'cause I don't think that was fair of her to say."
"Do you like when I make ____ for dinner?"
"Are you upset with me about ____?"
Ask him for feedback. Get specific if you need to. Men like direct questions. Don't be vague or expect him to read your mind.
And when he does talk, treat it like the best thing in the world that he trusts you enough to be open with you. Don't criticize. The more you reward his honesty with a desire to understand and help, the more he will say things rather than keeping them inside.