AITAH for telling a coworker I saw his wife with another man?

I work at a high school. I have 2 coworkers who are married, The husband has been there for a few years and the wife just came to our school last year. She is a 1:1 for a student and he teaches history.

The husband is really friendly and outgoing and talks to everyone, the wife not so much. She is not rude or anything, she keeps to herself in the special ed department. She loves the kids she works with but doesn't interact with much of the staff as far as I've noticed.

I was at the farmers market this weekend and saw the wife there with another man who happens to be a teacher at our school. They were laughing and just having a grand time eating, listening to music and shopping etc.

I went up and said hello, they said hello and made small talk for a minute and I left.

It just seemed odd, so I text her husband and told him that I saw his wife at the farmers market with "Mr Teacher" and they seemed to be very close.

My coworker text back with a laughing emoji and said "Mind your buisness. Those 2 idiots are friends. They love to go to the market and breakfast on Sunday. It's my day to sleep in and I hate the market she loves it and apparently he does to"

He made me feel like an idiot for telling him, but I know if my husband was out with another woman, I would want someone to tell me, even if it is "innocent". So AITAH for telling my coworker that his wife was out with another teacher?