Does this cross the line in marriage?

I found texts with statements from co worked female like "you are one of a kind, wish there were more men like you" and when my husband said he doesn't care if she looks rough today and her response is "you will when you wake up beside it" and he responds "haha quit it". Also her saying "I have such a great time whenever we are together" and his response is "me too☺". The texts are gone and he has no.idea how. Ha. What would you do? We have a 6 month old baby girl