I'd really love to have your valuable advice!
I have a professor who I respect very much and he adores me as his student, often says I'm his best student. And we kept in touch even after I graduated recently. I email him a lot about grad school and he usually responds really fast, like within 3 hours after I sent the email.
About two weeks ago, I wrote him an email about grad school, but he didn't reply. It was unusual but I waited for a week, and wrote two more emails to him and sent to both his email addresses, he still didn't reply. Now it's been two weeks. It's really unusual that he doesn't respond at all, and I normally CC myself in those emails, and I received my own emails, so I know it's not the problem of email delivery.
My concern right now is that he's old and I'm worried about his health; because him not responding is not like him. I'm in a different country now, so I can't physically check up on him, but I have his colleague's email. Would it be rude if I sent his colleague an email to ask if everything is okay with my professor? Do they have any news about him? What if my professor was just busy and didn'r reply? Would I be overboard on this issue by asking his collegue?
Also since he was gonna write me recommendation letters, would it seem like I'm only asking about him to make sure that I have my LOR? (WHICH ISN'T WHY I'M CONCERNED.) I don't know if it's appropriate to email his colleague and ask about how's he doing and if anything happened.
What should I do? Thank you so much!