Should I email my professor's colleague? 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!
I'm a professor, and two weeks is not a particularly long time for me to get around to replying to a non-urgent e-mail.  That said, I'm not generally as good at replying to e-mails (particularly those from former students, which you now are) as you describe your professor as being.

In your situation, I would do one or both of two things:


E-mail him again.  Say directly something like "I sent you a couple of e-mails over the past few weeks, but I haven't received a reply yet.  Could you please reply and let me know that you're all right, to put my mind at ease?"  A phrasing like this is less likely to come across as demanding, and more likely to come across as simply concerned.
E-mail his administrative assistant (not another faculty member) and ask whether Prof. X has been in to the department recently, or whether he is traveling or on vacation or the like.  You can say that you haven't heard from him in a while and you're starting to get concerned.  Administrative assistants are much more likely to know whether a particular professor is in town or out of town.  A random faculty member, on the other hand, is much less likely keep track of where your professor is;  I couldn't tell you what the details of my colleagues' schedules are.