My boyfriend replied to his ex gf’s text, what should I do and why?

Anonymous
So I found text message of his ex girlfriend texting him a sexy photo on his birthday night. His text message back said , “oh and no birthday wish all day”?

Is it appropriate for this to be happening? I mean he didn’t comment on her photo or anything. He just basically asked her why didn’t she wish him a happy birthday.

She responded that she didn’t get an invite so didn’t say anything.

What should I do and explain why?
My boyfriend replied to his ex gf’s text, what should I do and why?
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