My best friend went on a trip with girlfriend and came back acting distant. Should I ask him why?

Anonymous
Basically the title. He took a week long trip with his girlfriend of two months and came back different. He never wants to hang out with us, he’s not answering our text/phone calls anymore, he says he’ll do something and then doesn’t. I think what’s confusing me is that he only talks to me when we’re at work. We don’t work in the same department, but we are there on the same days. He’ll say hi to me update me on his life, but as soon as we’re leaving, it’s like he’s trying to avoid being seen with me. I want to ask him what’s going on, but I’m not sure if I should.
My best friend went on a trip with girlfriend and came back acting distant. Should I ask him why?
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